The _easy_ thing is probably also the thing that's hard to productionize: Just agree upon a secondary channel beforehand, and if I ever text/call/send you a sli

The _easy_ thing is probably also the thing that's hard to productionize: Just agree upon a secondary channel beforehand, and if I ever text/call/send you a slightly grainy video clip you and you're concerned if its really me asking for 50 amazon gift cards, you contact me via Channel 2. I don't think you can easily create a product to serve this, since _prior_ is the key there, and each pair of people should have their own preferred channels, since the scheme falls apart if the faker contacts you on Channel 2 first. If anything, centralizing on that part just creates a massive vulnerability.