I FOUND A CHEAT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ok, this uses motion analysis, but if you want to get >1000% truthful, heres what you do:
Before you tap “next,” shake your iPhone/iPod.
While youre shaking it, tap “next.”
Keep shaking it and tap “Show Results.”
Then the percentage should keep on incresing until who knows when.

This works because you started and ended with the same motion so it naturally thinks being shaky is your neutral motion.

Who, Me? Yes, You! about LIE DETECTOR... FREE!