A keyboard called WOWKeys is trying to make good use of your little touchscreen-based iPhone when it's just sitting there charging itself up. The keyboard includes an actual iPhone dock, and with a switch on the device, you can go from controlling your computer wirelessly to using the keyboard on the phone. The US$100 USB keyboard even has a set of hotkeys that allows you to control things like song changing, volume, and even go to your iPhone's home screen straight from the keyboard itself.
And depending on the apps you have loaded, you can of course use the iPhone to control any number of other devices, as it obviously works as usual while plugged in. My iPhone does sit next to me all day (and I will sometimes pull it up while a program is loading on my Mac to play a quick game or check Twitter), but a dock like this might help me include it in my workflow a little more officially. $100 is perhaps a bit steep, but it's an interesting device.