SMS & email only 'phone'

I wondered how hard it would be to take a GSM module, couple it with a small querty keyboard and still have a thin form factor.

The advantage to this would be:

  • as a separate device, you'd have a battery backup for your smartphone
  • you can turn the phone off and have it check for messages in intervals of say 10mins. This would mean the battery would last a lot longer
  • you can use an old green LED screen (or partial updating eink?)
  • if it was thin enough you could velcro it to the back of your main phone... or just not carry a phone at all (some people only do SMS and txt to save cash)

I think this is too difficult to do well.
I looked at adapting current phones but I'm finding it's either too big or too new.

An update to this tutorial is needed:
http://tronixstuff.wordpress.com/2011/01/19/tutorial-arduino-and-gsm-cellular-part-one/

Your thoughts?