Just noticed this in the Ovi Store, HWKey is a small and free utility to launch any designated application from your phone's camera (hardware) button. For anyone more interested in launching PhoneTorch or Gravity (etc) than Camera, this is a great little addition to your smartphone. Screens below...

Here's the Ovi Store entry, plus a couple of screens. Note the option to auto-start, so you don't have to remember to start this (and leave it running) manually every time your phone gets restarted. Very handy.