I was at my local store yesterday. It didn't take long for me to notice this guy (next to me) was using a device to keep the count. As each card hit the felt, he would push buttons using his left hand which was inside his jacket pocket.

At the shuffle, he pulled out his phone, then pulled out this device with other hand (kept under table). It was a small key fob with 2 buttons (they appeared to be unmarked). I was able to take a quick glance. He saw me look, then left the table shorty after.

Man, this dude is an idiot. It's only a matter of time before he scores a pair of handcuffs.