A few months back I posted about making my own RC controller: http://diydrones.com/profiles/blogs/diy-rc-controller
I finally got around to making it work. I am very happy with the results! I ended up using code posted on RCgroups to format the PPM signal: http://www.rcgroups.com/forums/showthread.php?t=1808432&pp=100
Making your own transmitter is pretty easy. I can now program everything exactly as i need. For example, the shutter control for my NEX5 requires a momentary button that is not held down... I can now format the command from the transmitter to switch for the correct amount of time.
Hope you enjoy,