Square has begun a limited public beta test of its iPhone-based payment system. In exchange for using the service, people must currently share details such as bank information, and the specific ID of their iPhone or iPod touch. The company is promising those signing up for a Square payer account that a penny from each transaction made will be sent to a charity of their choice.

The Square technology revolves around a dongle that plugs into an iPhone or iPod's headphone jack. The cube scans a payer's credit card, sending the data to an online processing service. An assigned photo can be used to confirm a person's identity, and receipts can simply be e-mailed instead of printed. A full-scale deployment of Square is planned for later this year.