, the startup behind a potentially game-changing mobile add-on that turns your phone into a portable credit card payment system, is best known thus far for the involvement of Twitter founder Jack Dorsey
. I have a feeling Square is going to be a ubiquitous sight within the next couple of years, though, because it's just so dang useful. For small businesses or points of sale where it's just not practical to have a full-sized credit card scanner - I'm thinking concert merch booths, farmers' markets, and beyond - Square could result in a lot of additional sales to customers who don't carry cash.
Of course, that means a nice revenue stream for Square, which takes a small fee for each transaction. As far as the physical device, manufacturing costs are reportedly low enough to make it cheap, or maybe even free. If you want to be one of the first to give Square a try, you can put your name on the list
for the closed beta now. Square is starting out on the iPhone for the time being, with plans to expand to other devices in the future.