I'm not aware of any other "apps" but there are multiple ways to gift bitcoin.
OpenDime, ask the receiver to set up a wallet and send him the bitcoin, print a paper wallet, and hand it to the receiver etc.
I like the idea, but are you planning on making this open source though? I guess not? since it you're going to be adding swapping, amazon gift cards, and other stuff?
I was thinking that asking someone to download an app adds a considerable amount of friction to the process, but I could be wrong about that assumption. Oh yeah it would be open-source, I would not do bitcoin any other way.