As far as we know there isn't a third party app that offers 48 or 60 frames per second (HFR) video capture on the iPad. SloMo used to offer 60fps capture on iPhone hardware at 720p, but that feature never quite made its way to the iPad.
We are hoping that the recent interest in high framerate video capture, thanks to the HFR cinematic release of The Hobbit, might create a swell of public interest in HFR video capture. HFR certainly would not be ideal for every scenario, but it would be very handy to at least have the option, right there in the default camera app, to switch to HFR mode. Of course iMovie would have to support HFR too... come to think of it, HFR would be perfect for some stunning iMovie slow motion video effects too!