I have an Erostek ET-312 which is supposed to be the best out there. It's quite pricey for starters but I haven't seen any unit out there that can match the flexibility of this unit. It has different setting and allows you to modulate the frequency of the electrical pulses as well as the intensity. You can even get it to respond to sound by using a mic or by using sound files. I purchased an anal probe, and a sparkler (an 8 inch rubberized sound for insertion into the urethra) and a cage that goes around your cockhead with an inch long sound that is inserted into the urethra. Pretty intense stuff. If you're looking for a hands-free experience, this is certainly one way to accomplish it. IMO its only dangerous if you position the two contacts such that your heart is between the two. Other than that, its safe.