Honestly the one on my phone is more for fun than anything else - I use it to show people that LLMs can run on personal devices but rarely do anything useful with it.

I use the MLC Chat app from the App Store: https://apps.apple.com/gb/app/mlc-chat/id6448482937

My favourite example prompt for demos is "Write an outline of a Netflix Christmas movie where a topical-profession falls in love with another topical-profession" - customized for the occasion.

e.g. "Write an outline for a Netflix Christmas movie set in San Gregorio California about a man who runs an unlicensed cemetery falling in love with a barrister at the general store" - result here: https://bsky.app/profile/simonwillison.net/post/3ldthrqb6c22...