It's subconsciously getting drummed into us from all sides, but just in case you haven't heard it yet: the Nokia N900 is the most hackable phone around. It may not be the best phone, but it sure is open source.
A blogger at DoItDifferent created a widget for the N900 using Shutter—which uses LIRC to control the Nikon remotely—and Flashlight, which turns the N900's flash into a torch. Then, using the IR transmitter in the phone, it paired up with the Nikon D40's IR receiver for the remote shutter release. When the widget was clicked on the N900, the LED flash strobed and the D40 was triggered, taking a photo instantly.