Maybe ESPerfect or perhaps any type of impression device possibly. As D ICE R said though, be more specific about it though and don't say street magic mentalism. That just sounds dirty and just a bad name for mentalism.
Straight out of Corinda, A Swami Gimmick and a business card. Take out the card ask them to think of a number between 1 and 1000. "Oh you thought of 649, is there any reason you thought of that number. I wrote something on the back of this business before I asked you to think of that number..."
Freaking killer stuff cause not only do they have no where to go as far as how this sort of thing could be done, but now they have not only your credentials, but also a story to tell there friends and your credentials as evidence of the wrongful story also.
I'm not a mentalist by trade, but I couldn't tell you how many more shows I have acquired with that one trick.
Well as Morgician once told me, "I could walk into a restaurant and take a poop on the table and get reactions."
I believe it would be better to say astonish, of course it's up to you.
A few good walkaround effects would be:
Killer Elite Zone Pro
Looch's material has a ton of stuff that's great for walkaround. Easy, simple, direct which is exactly what mentalism should be.
My only rule with mentalism is simple and direct just like Looch would do, you don't want too long of a script, just ignore want you see Derren Brown do on TV he almost always uses pre show work which works great but your language skill have to be perfect for that kind of work, I did try it before and it didn't work cause the guy say "sure you know i wrote it on your pad a few moments ago."
I'm curious as to how using iForce would look tacky and/or silly. It's the modern equivalent of using a pen and paper (not carrying paper and a pen on me is precisely the excuse I use to justify the use of the iPod Touch, actually). It just looks like a drawing application, and functions like one, as well. The Doodle application, without the magical secret, is even available on the iTunes store, to further camouflage the fact that you're using a "magic" app, just in case you have a spectator that's really interested in learning how you did it (although, I really can't see someone going through the effort of trying to search up the app you used--although, I suppose it's entirely possible).I'd advice against using things like the Iforce or any other sort of Iphone app. It just looks tacky and silly.