we tried a mobile with DS but it didn't really work - it supposedly had a remote to activate it wirelessly from the door but that only worked at night when there was no ambient light (it was light activated somehow - daylight reduced the beam somehow). A Fisher Price jungle theme one from memory - currently packed away while I think about what to do with it. It was also chunky on the set up on the side of the cot - we had to have the cot out from the wall a bit to get the thing to attach mainly because we couldn't attach it to the end of the cot because of the design of the cot. It was also supposed to convert to being able to use on the bench/cupboard top and put rotating lights on the roof (unfortunately the spot we had to put it didn't really work when it was converted and it was just too big to take up the valuable flat space we had.) DS wasn't really into it in the end we just packed it up and put it away. I think we had it in his cot from about 1 month-ish to about 7/8 mths when he started to grab it and pull on it.

I don't think I've really helped have I? I would make sure you didn't get a chunky attachment section one (I can't think of what else to call that bit). If I was going to try it again with the next one, I'd probably just get one of those light projectors or make a fairly basic one myself or hang one from the ceiling rather than trying to have one to attach to the cot.