TL;DR this is about using your cellphone - *caller name from your phonebook* - as prop in magic.

A friend explained how he plays with a young relative; pretending his phone is a lie detector.
He holds the phone and presses the power button to get the screen to light up. I asked him if it shows caller id or saved nicknames. It does... so...
and if you happen to know a published reference to this notion please post it below. Thanks. -JonT

If you know someone and they are open to helping with a trick:
* Temporarily change their nickname in your phone directory to be "Liar" or "Nope" or such...
And if your friend does not have you on speed dial - help them get that set up.
So, when the time comes your phone can be on the table and -they can speed dial your number and the nickname will show on your phone screen. Yes, ringtones are useful too