Why limit the amount? The main benefit of V4V is that it's unlimited to the upside.
Amethyst v0.15.1: Zaps
Few Things first:
1. This is an early release. You can send and receive zaps with a fixed amount (1000 sats) and see those received zaps in user's profile and in your notifications. Sending is a bit too slow. More options will be coming.
2. The receiver MUST use Zap-supported lightning address setup to work. Otherwise, you would just send a lightning tip and the amount will not update on the screen.
3. The only lightning service that seems to be easily compatible with Zaps is https://strike.army You can connect your Strike wallet there and they will manage the Zap reply in Nostr for you. Your lightning address will look like user@strike.army
Download: https://github.com/vitorpamplona/amethyst/releases/download/v0.15.1/app-release-v0.15.1.apk