I'm just thinking of Jack's teleporter/time travel thing, but it's quite a bit bigger than your normal watch. I also don't see the teleporter, just the watch. Whereabouts did you see the time jumper thingy?

And after checking The Pandorica Opens, I'm pretty sure that's the time jumper thing. Much smaller than Jack's, yes, but it still looks too big to be the Second Doctor's leather watch. To me, at least.