Synchronoss Technologies has agreed to pay as much as $75 million to acquire FusionOne, a maker of software that lets users back up and synchronize their mobile data.

Bridgewater, N.J.-based Synchronoss makes software that manages instantaneous transactions, allowing the automation of subscriber activations. It will pay $40 million for FusionOne at the outset, with $32 million of that in cash and $8 million in Synchronoss stock. Synchronoss will also pay as much as $35 million in cash and stock if FusionOne hits its targets through 2011. The deal is expected to close this month.

FusionOne has interesting technology because its sync software can back up data as well as transfer it from one phone to another. That means it could theoretically be used to move your mobile content such as pictures from one phone to another, and even from one carrier to another. But FusionOne’s customers primarily use it back up data or to transfer data from an old phone to a new phone when upgrading at the same carrier. Because FusionOne lets users painlessly upgrade, its technology is critical in retaining and growing carrier revenues.

FusionOne has more than 40 issued and pending patents and it supports more than 600 cell phones across numerous mobile platforms. Customers include Verizon Wireless, Cellular South, CenturyLink, Bell Mobility and AT&T. Synchronoss said the deal will strengthen its patent holdings, diversify its business, and expand its value to retailers. The company expects FusionOne to add $8 million to $10 million in revenue in the second half of 2010.

FusionOne, based in San Jose, Calif., was founded in 1998.

Don’t miss MobileBeat 2010, VentureBeat’s conference on the future of mobile. The theme: “The year of the superphone and who will profit.” Now expanded to two days, MobileBeat 2010 will take place on July 12-13 at The Palace Hotel in San Francisco. Register now. Tickets are going quickly. For complete conference details, or to apply for the MobileBeat Startup Competition, click here.