You're basically describing one aspect of lightning and most layer 2's. If you boil it down they're basically deferred settlement of pre-signed transactions.

Like all layer 2s that operate this way, Party1 can steal from Party2 by spending the funds they've transferred in another transaction effectively double spending them. So in addition to pre-signed transactions, L2's usually have some mechanism for fighting such double spending.

Open Dime is a cool riff on this. Party2 will only accept an Open Dime from Party1 if the device hasn't been tampered with, because it suggests Party1 never had access to the key that could spend the utxo on the Open Dime.