diff --git a/README.md b/README.md
index 8535cc7..180b7c7 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,10 @@ To then update your firmware, simply run the following command as root:
 rpi-update
 </pre>
 
-By default, the 224MB memory split will be used. If you'd like to use the 192MB split, then type:
+
+By default, rpi-update will attempt to determine the split you're currently using, and then use that split. If it cannot determine what split you are using, it will default to 224MB.
+
+If you'd like to explicitly select a split, simply provide the RAM split value after the command as follows:
 
 <pre>
 rpi-update 192
@@ -32,3 +35,28 @@ If you'd like to use the 128MB memory split, then the command is the same as the
 After the firmware has been sucessfully updated, you'll need to reboot to load the new firmware.
 
 This tool is experimental, and may screw up your install. If you have problems with it, post an issue to this GitHub repo and I'll see if I can help you.
+
+Expert options
+--------------
+
+There are a number of options for experts you might like to use, these are all environment variables you must set if you wish to use them.
+
+### SKIP_KERNEL
+
+#### Usage
+
+SKIP_KERNEL=1 rpi-update
+
+#### Effect
+
+Will update everything EXCEPT the kernel.img files and the kernel modules. Use with caution, some firmware updates might depend a kernel update.
+
+### ROOT_PATH/BOOT_PATH
+
+#### Usage
+
+ROOT_PATH=/media/root BOOT_PATH=/media/boot rpi-update
+
+#### Effect
+
+Allows you to perform an "offline" update, ie update firmware on an SD card you're not currently booted from. Useful for installing firmware/kernel to a non-RPI customised image. Be careful, you must specify both options or neither. Specifying only one will not work.
diff --git a/rpi-update b/rpi-update
index ba1a229..6ac76b5 100755
--- a/rpi-update
+++ b/rpi-update
@@ -3,94 +3,188 @@
 set -o nounset
 set -o errexit
 
-UPDATE=${2:-1}
-UPDATE_URI="https://raw.github.com/Hexxeh/rpi-update/master/rpi-update"
+UPDATE=${UPDATE:-1}
+UPDATE_URI="https://github.com/Hexxeh/rpi-update/raw/master/rpi-update"
+
+ROOT_PATH=${ROOT_PATH:-"/"}
+BOOT_PATH=${BOOT_PATH:-"/boot"}
+SKIP_KERNEL=${SKIP_KERNEL:-0}
 FW_REPO="git://github.com/Hexxeh/rpi-firmware.git"
-FW_REPOLOCAL="/root/.rpi-firmware"
-FW_PATH="/boot"
-FW_REPONAME=`basename ${FW_REPOLOCAL}`
-FW_RAM=${1:-224}
-FW_GPU=$((256-FW_RAM))
+FW_REPOLOCAL="${ROOT_PATH}/root/.rpi-firmware"
+FW_PATH="${BOOT_PATH}"
+FW_MODPATH="${ROOT_PATH}/lib/modules"
+FW_RAM=${1:-0}
+GITCMD="git --git-dir=\"${FW_REPOLOCAL}/.git\" --work-tree=\"${FW_REPOLOCAL}\""
+
+function detect_split() {
+	if [[ -f "$FW_PATH/start.elf" && ${FW_RAM} -eq 0 ]]; then
+		FW_RAM=224
+		for R in 128 192 224
+		do
+			if [[ -f "$FW_PATH/arm${R}_start.elf" ]]
+			then
+      				if diff "$FW_PATH/arm${R}_start.elf" "$FW_PATH/start.elf" >/dev/null
+      				then
+        				FW_RAM=$R
+        				break
+      				fi
+			fi
+		done
+	fi
+	FW_GPU=$((256-FW_RAM))
+}
 
 function update_self() {
-	echo "Performing self-update" 
+	echo "Performing self-update"
 	_tempFileName="$0.tmp"
-	_payloadName="$0.payload"
- 
-	if ! wget --quiet --output-document="$_payloadName" $UPDATE_URI ; then
+
+	if ! wget --quiet --output-document="${_tempFileName}" "${UPDATE_URI}"; then
 		echo "Failed to download update for rpi-update!"
 		echo "Make sure you have ca-certificates installed and that the time is set correctly"
 		exit 1
 	fi
- 
-	_interpreter=$(head --lines=1 "$0")
-	echo $_interpreter > "$_tempFileName"
-	tail --lines=+2 "$_payloadName" >> "$_tempFileName"
-	rm "$_payloadName"
- 
-	OCTAL_MODE=$(stat -c '%a' $0)
-	if ! chmod $OCTAL_MODE "$_tempFileName" ; then
-  		echo "Failed: Error while trying to set mode on $_tempFileName."
+
+	OCTAL_MODE=$(stat -c '%a' "$0")
+	if ! chmod ${OCTAL_MODE} "${_tempFileName}" ; then
+  		echo "Failed: Error while trying to set mode on ${_tempFileName}"
 		exit 1
 	fi
 
-	cat > updateScript.sh << EOF
+	cat > /tmp/updateScript.sh << EOF
 	#!/bin/bash
-	if mv "$_tempFileName" "$0"; then
-		rm -- \$0
-		exec /bin/bash $0 ${FW_RAM} 0
+	if mv "${_tempFileName}" "$0"; then
+		rm -- "\$0"
+		exec env UPDATE=0 /bin/bash "$0" "$@"
 	else
 		echo "Failed!"
 	fi
 EOF
- 
-	exec /bin/bash updateScript.sh "$@"
+
+	exec /bin/bash /tmp/updateScript.sh
 }
 
 function update_modules {
-	cp -R ${FW_REPOLOCAL}/modules/* /lib/modules/
-	for D in `find ${FW_REPOLOCAL}/modules -mindepth 1 -maxdepth 1 -type d`; do
-		depmod -a `basename $D`
-	done
+	if [[ ${SKIP_KERNEL} -eq 0 ]]; then
+		cp -R "${FW_REPOLOCAL}/modules/"* "${FW_MODPATH}/"
+		find "${FW_REPOLOCAL}/modules" -mindepth 1 -maxdepth 1 -type d | while read DIR; do
+			depmod -b "${ROOT_PATH}" -a $(basename "${DIR}")
+		done
+	fi
 }
 
 function update_sdk {
-	ELFOUTPUT=`readelf -a /bin/bash`
-	if [ "$ELFOUTPUT" != "${ELFOUTPUT/VFP_args/}" ]; then
+	if [[ -f /etc/init.d/vcfiled ]]; then
+		/etc/init.d/vcfiled stop
+	fi
+
+	ELFOUTPUT=$(readelf -a "${ROOT_PATH}/bin/bash")
+	if [ "${ELFOUTPUT}" != "${ELFOUTPUT/VFP_args/}" ]; then
 		echo "Using HardFP libraries"
-		cp -R ${FW_REPOLOCAL}/vc/hardfp/* /
+		cp -R "${FW_REPOLOCAL}/vc/hardfp/"* "${ROOT_PATH}/"
 	else
 		echo "Using SoftFP libraries"
-		cp -R ${FW_REPOLOCAL}/vc/softfp/* /
+		cp -R "${FW_REPOLOCAL}/vc/softfp/"* "${ROOT_PATH}/"
+	fi
+	cp -R "${FW_REPOLOCAL}/vc/sdk/"* "${ROOT_PATH}/"
+
+	if [[ -f /etc/init.d/vcfiled ]]; then
+		/etc/init.d/vcfiled start
 	fi
-	cp -R ${FW_REPOLOCAL}/vc/sdk/* /
 }
 
 function set_split {
-	cp ${FW_REPOLOCAL}/arm${FW_RAM}_start.elf ${FW_PATH}/start.elf
+	cp "${FW_PATH}/arm${FW_RAM}_start.elf" "${FW_PATH}/start.elf"
 }
 
 function update_firmware {
-	cp ${FW_REPOLOCAL}/*.elf ${FW_PATH}/
-	cp ${FW_REPOLOCAL}/*.bin ${FW_PATH}/
-	cp ${FW_REPOLOCAL}/*.img ${FW_PATH}/
+	cp "${FW_REPOLOCAL}/"*.elf "${FW_PATH}/"
+	cp "${FW_REPOLOCAL}/"*.bin "${FW_PATH}/"
+	if [[ ${SKIP_KERNEL} -eq 0 ]]; then
+		cp "${FW_REPOLOCAL}/"*.img "${FW_PATH}/"
+	else
+		echo "Skipping kernel/modules updated as requested"
+	fi
 }
 
 function finalise {
-	ldconfig
+	ldconfig -r "${ROOT_PATH}"
+	eval ${GITCMD} rev-parse master > "${FW_PATH}/.firmware_revision"
 	sync
 }
 
-if [[ $EUID -ne 0 ]]; then
+function download_repo {
+	echo "Setting up firmware (this will take a few minutes)"
+	mkdir -p "${FW_REPOLOCAL}"
+	git clone "${FW_REPO}" "${FW_REPOLOCAL}" --depth=1 --quiet
+	RETVAL=$?
+	if [[ ${RETVAL} -ne 0 ]]; then
+		echo "Failed to download new firmware files"
+		exit 1
+	fi
+}
+
+function update_repo {
+	echo "Updating firmware (this will take a few minutes)"
+	eval ${GITCMD} fetch --quiet
+	RETVAL=$?
+	if [[ ${RETVAL} -ne 0 ]]; then
+		echo "Failed to download updated firmware files"
+		exit 1
+	fi
+	eval ${GITCMD} merge origin/master -m "automerge" --quiet
+	RETVAL=$?
+	if [[ ${RETVAL} -ne 0 ]]; then
+		echo "Failed to download updated firmware files"
+		exit 1
+	fi
+}
+
+function do_backup {
+	cp -a "${FW_PATH}" "${FW_PATH}.bak"
+	cp -a "${FW_MODPATH}" "${FW_MODPATH}.bak"
+}
+
+function do_update {
+	update_firmware
+	update_modules
+	update_sdk
+	set_split
+	finalise
+	echo "If no errors appeared, your firmware was successfully $1"
+	if [[ "${ROOT_PATH}" == "/" ]]; then
+		echo "A reboot is needed to activate the new firmware"
+	fi
+}
+
+if [[ ${EUID} -ne 0 ]]; then
 	echo "This tool must be run as root"
 	exit 1
 fi
 
-if [[ $UPDATE -ne 0 ]]; then
-	echo "Raspberry Pi firmware updater by Hexxeh"
+if [[ ${UPDATE} -ne 0 ]]; then
+	echo "Raspberry Pi firmware updater by Hexxeh, enhanced by AndrewS"
 	update_self
 fi
 
+if [[ ( "${ROOT_PATH}" == "/"  &&  "${BOOT_PATH}" != "/boot" ) ]] ||
+[[ ( "${BOOT_PATH}" == "/boot"  &&  "${ROOT_PATH}" != "/" ) ]]; then
+	echo "You need to specify both ROOT_PATH and BOOT_PATH, or neither"
+	exit 1
+fi
+
+if [[ ! -d "${FW_PATH}" ]]; then
+	echo "${FW_PATH} doesn't exist"
+	exit 1
+fi
+if [[ ! -f "${FW_PATH}/start.elf" ]]; then
+	echo "${FW_PATH}/start.elf doesn't exist."
+	exit 1
+fi
+if [[ ! -d "${FW_MODPATH}" ]]; then
+	echo "${FW_MODPATH} doesn't exist"
+	exit 1
+fi
+
 command -v git >/dev/null 2>&1 || {
 	echo "This tool requires you have Git installed, please install it first"
 	echo "In Debian, try: sudo apt-get install git-core"
@@ -105,35 +199,25 @@ command -v readelf >/dev/null 2>&1 || {
 	exit 1
 }
 
-echo "Using memory split of ${FW_RAM}MB/${FW_GPU}MB"
+detect_split
+if [[ ${FW_RAM} -ne 224 ]] && [[ ${FW_RAM} -ne 192 ]] && [[ ${FW_RAM} -ne 128 ]]; then
+	echo "RAM value must be one of: 224, 192, 128"
+	exit 1
+fi
+echo "Using ARM/GPU memory split of ${FW_RAM}MB/${FW_GPU}MB"
 
-GITCMD="git --git-dir=${FW_REPOLOCAL}/.git --work-tree=${FW_REPOLOCAL}"
-
-mkdir -p ${FW_REPOLOCAL}
-if $($GITCMD rev-parse &> /dev/null); then
-	echo "Updating firmware (this will take a few minutes)"
-	$GITCMD fetch --quiet
-	$GITCMD merge origin/master -m "automerge" --quiet
-	update_firmware
-	update_modules
-	update_sdk
-	set_split
-	finalise
-	echo "If no errors appeared, your firmware was successfully updated"
-else
-	echo "We're running for the first time"
-	echo "Setting up firmware (this will take a few minutes)"
-	cp -R ${FW_PATH} ${FW_PATH}.bak
-	git clone ${FW_REPO} ${FW_REPOLOCAL} --depth=1 --quiet
-	RETVAL=$?
-	if [[ $RETVAL != 0 ]]; then
-		echo "Failed to download new firmware files"
-	else
-		update_firmware
-		update_modules
-		update_sdk
+if [[ -f "${FW_REPOLOCAL}/.git/config" ]]; then
+	update_repo
+	if [[ -f "${FW_PATH}/.firmware_revision" ]] && [[ $(cat "${FW_PATH}/.firmware_revision") == $(eval ${GITCMD} rev-parse master) ]]; then
+		echo "Your firmware is already up to date"
 		set_split
 		finalise
-		echo "If no errors appeared, your firmware was successfully setup"
+	else
+		do_update "updated"
 	fi
+else
+	echo "We're running for the first time"
+	download_repo
+	do_backup
+	do_update "setup"
 fi