I also found it to be an almost unexplainable item therefore highly suspicious.
I think Peter Nardi's Stealth Wallet is tonnes better.
I agree if your doing impromtu magic, but for table hopping or the like, there are no such problems.
So in an impromtu situation, yeah I'd go for the stealth or similar, but for table hopping the Thought Transmitter is the business. Also in regards to the unexplainable bit, I use it with "post it" notes and it looks for all the world like a little "post it" note holder.
Thought transmitter also has the advantage of being examinable ( within reason ) and has far cleaner handling.