Using an on-board camera should be legal as long as all other rules are also followed. see here,
http://www.chiefdelphi.com/forums/sh...94&postcount=3
In some cases I can understand FTA's or officials requesting that you not use them because they are not familiar with how these cameras function. But assuming you are able to show that they meet all other rules I don't see why you wouldn't be able to use one.