Tiny enough to be relatively inconspicuous and still accessible. I was hoping for something about the size of my thumb that doesn't require its own separate power supply.

I did plenty of Googling before posting and haven't found it, yet. Maybe my Google Fu just isn't strong enough, yet.


Ah, something: This would work, but it's $23 and a little on the big side:



http://electronicsusa.com/mk1and2.html