An inexpensive battery powered kitchen clock with a sweep second timer makes an easy to acquire and use process timer. Just make sure to get one with clear numerals and a black (not red) sweep second hand.
To reinforce your discipline, I'd suggest that much of the development time be spent with the image facing down, not up!
I use a digital kitchen timer with an LCD screen. It isn't always easy to read (needs a little light), but it won't fog my paper. +1 for face down (though I do watch some things just 'cause it's still cool).
Keep in mind that it could be chemicals on your fingers, too, and I second the tongs.