Oral-B professional care has been my weapon of choice for almost 15 years and it seems to be the standard around here according to the people I talk to. I use it on my wife; she usually starts gnashing her teeth after 1 second and begins to cry after 1 minute. You can use it on many different parts of the body but the toes produce the best results; however you might wanna use a strict method of bondage as your 'lee will buck A LOT. Honestly I think my wife's head would hit the roof if I didn't restrain her. Turning it on is enough to make her lose it: upon hearing the sounds she immediately starts to beg.
The great thing about this toothbrush is that it's a two-in-one tool. The bristles are enough to drive a woman crazy but there's more to it. You can remove the head; beneath, there's a metallic "axis" of sorts which allows for very high precision tickling. Seriously, that thing is the tickling equivalent of a scalpel. Drag it very slowly across the balls of the feet, just underneath where the toe stems meet the foot, or draw insistent circles on the same area over and over, and watch a human being abandon all notions of dignity
I'd like to try one of those sonic brushes. I wanted to buy one for Christmas, but my wife deemed it an unnecessary expense given that the other tool is already torture enough and those things don't come cheap.