Another similar company to keep an eye out for is ShopKeep POS. http://www.shopkeep.com/shopkeep-vs-square Found it at the Temple Coffee shops.

I actually enjoy using their interface a lot more than Square, and it seems to be more feature rich on the merchant end too. The main thing I have fun with is the ability to print your signature onto the receipt!

It would be interesting to look into all the developers of these POS swipe machines. What companies fund them? Credit card companies? Grocery store corporations? Just pure profit from sales of the devices? I know I see a lot of innovation on grocery store registers, and a lot of the visa swipe devices have been upgrading their interfaces consistently every few years.