You could try these sunglass cameras. Only problems that could arise is that the eye glass part may not withstand impacting BB's, and the camera itself might take a direct hit, but that could also be said about any other mounted camera system. I suppose you could always wear these underneath a full face mask or other eye protection.
http://www.ebay.co.uk/itm/360626042430?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
Just thought I'd add: There's a pretty good high quality video review of a more expensive set of sunglasses camera. Recorded footage seems the mutts.