hi there!
im now writing some acts, and i have a great one -
im looking for a cellphone in the audience, taking one up on the stage, places his phone inside a hanky. im taking a 5K hammer and crushing his phone. now im telling him to look inside this bag, and say if it's his cellphone inside. he finds only a bag of chips. you ask for his number and call, the chips starts to ring. he opens the bag and find his phone sealed inside.

now - what can i do with the hankey and the crushed phone?

I dont think i understood this correct, but what you can do is vanish the hankey by using a TT or making it turn into a cane, and if you meant "crushed CHIPS" you can make them somehow turn back into a regular sized chip and then eat it. I'm sure you can come up with that, just be creative...

Well that's a neat effect, where would I pick that up at?

nowhere

it's a simple twist on the old watch-crush trick.