Pretty sweet idea;) You better have copyright on that, I'm gonna nick it;). Only Joking.
But then we could use money.

I think something could interfere and steal random peoples money

But would there be multiple doors and lines also what if people dont have the money and keep putting stuff down.?? Or what if say you were with your friend and she paid and not you and she got mad.

then we cant steal stuff

Technology always has its glitches.

See that doesn't make sense because if the item was 5 and you only have 2 what if you originally had 7 dollars and actually paid for the item? There is no way to see transactions of the car through your invention

This is a great idea patent it right now!

Nice idea but it would be hard to get this system to work out correctly.

That would be a good invention but how would you make this invention for food for example? I don't think the invention could detect an apple, you'd have to put a sensor on it or something.

I could see the invention working on electronics but not a grocery store.

Good luck getting this idea to be adopted by the companies.