A framework to keep an eye on: http://www.phonegap.com
- access the camera
- access the contact list
- get geolocation information
- read acceleration data
- creating beeps and vibrations
The great thing is that no complicated Java or Objective C development is needed to make powerfull applications... It works for most major mobile devices: iPhone, Android, Palm Pré, Symbian, Blackberry and in the future Windows mobile.