I have thought for YEARS that there needs to be an app for that.. easy NFC or BT or QR code app that can easily do a quick share, without having to really exchange any user specific credentials. Obviously one has to authenticate, but being able to pull up my phone or Apple Watch (or whatever device you have) and tap 3, 5, 10$ and send to the nearest device (with confirmation fo course) is where we need to go.

till the, yeah I keep an envelope of 1’s and 5’s in the car, which is dumb.