Here is a Bluetooth 2G/3G display client concept from the early '00's. This thing would have been a keyboarded, large(er) screen, short range companion to the ultra thin Razr phone in your pocket. There was a chunky version that would run an emulator when you stuffed in one of those Gameboy Advance cartridges popular at the time.
This old pager sized guy begs the question of how you might want to build something using the phone as Wifi/Bluetooth Hotspot concept today? I might take everything out of a laptop you possibly could, which would make it pretty much just the thickness of the display & keys(or these days, just ditch the keyboard altogether, iPad style). That leaves rendering/client hardware, touchpad sensing, and your Bluetooth(or Wifi) 'X-win' link to your phone providing the local apps processing. If you were careful with the short range wireless display compression, you could probably build a cheap tablet style terminal that blows up whatever is running in your phone. The wireless display stuff Intel had on display @CES2010 could maybe work here, in the forward direction, I think they are missing the reverse link for control info going back to the phone.
I'll probably try and do a video on this in the near future.
Anthony