The Handshake Deal Protocol
Why not do something creative like have the investor sign a dollar bill (of any denomination) and give it to the founders?Every founder comes prepared with some cash in their wallet, and then when you confirm a deal the founders ask the investors to sign the dollar bill with a Sharpie/pen.  On it would be some sort of short-hand for the deal valuation... Cash is more ubiquitous than phones - even impromptu, it's highly likely one person will have a cash on them - plus you don't have to deal with sharing emails, phone signal, phone battery, waiting for that text/email message to come through, blah-dee-blah.And then you can frame it and do all sorts of other creative/cutesy stuff.  If YC made it a tradition to do a "signed cash" deal as a way of indicating the confirmation of a deal, it'd make for a cool way of looking back at all the great (or not-so-great) investments... sort of like that whole "my first dollar" thing some people do.