I had this idea some time ago but due to tribe's new policies I can't suggest what one could do with a pen like this. Initially the suppliers I found wanted an exhorbitant sum, but now I found a place where you can get them for five bucks a pop. I think I CAN say that one could disguise the letters on the pen with paint or tape and then one of these could be left somewhere attached to a string. Yah. I think I can say that. For the rest, use your imagination. It could really inconvenience certain "people".

www.shomer-tec.com/site/product.cfm

Swaz