Check out ALDLdroid. I'm not sure what the refresh rate is for most of the Bluetooth adapters but a lot of the homebrew stuff I've seen is a little slow for a cluster replacement
I've been messing with OBDII over Bluetooth with a Raspberry Pi, using a Pi or Arduino makes it easier to add additional aftermarket sensors down the road:
OBDII is a lot more standardized and well documented but I'm sure it would be possible to do the same for OBDI