Send a text message to a particular number and it comes out of a cheap receipt printer sitting on my desk at the studio.
That is the whole thing. The message arrives as an SMS, gets handed to a small Go program, and goes out over the network to the printer as ESC/POS, which is the same protocol every point of sale terminal has used for decades. It will do QR codes too, so a link can arrive as something you scan rather than something you retype.
There is no product here and no problem being solved. It is a physical inbox that makes a noise, and getting a receipt from a friend is much funnier than getting a text.