As far as I know: If you have an index shifter the derailer has to work with the shifter. sheldonbrown.com probably has info you need. The front and rear gearing are standard.
If you have friction shifters it probably does not matter as long as the shifter can reach all the gears.
2000 Montague CX, I do not recommend it, but still ride it.
Strida 3, I recommend it for rides < 10mi wo steep hills.
2006 Rowbike 720 Sport, I recommend it as an exercise bike.
1996 Birdy, Recommend.
Wieleder CARiBIKE (folding), decent frame.