According to Mac's Football Blog, The Patriots have signed former Dolphins CB Will Allen to a one year deal. Allen is 5-10, 196 lbs and will be 34 at the start of next season. The Patriots had worked out Allen early last season, but didn't sign him.
Allen is old, but he has some potential value. In 2009, he played free safety before injuring his ACL and ending his season. He was placed on the IR for all of 2010 and came back to play slot corner for the Dolphins in 2011.
According to Pro Football Focus, Allen was a top five slot corner in the league last season. His 419 slot snaps were #1 in the league. He was targeted while in coverage once every 7.1 snaps for 5th best in the league. He allowed 0.81 yards per coverage snap for 3rd best in the league. He allowed a reception once every 11.6 coverage snap for 6th best in the league.
Since Allen will be 34 and is on a one year deal, he'll most likely be a camp body who has to prove his worth for a roster spot. While he most likely has an outside shot, his versatility and high level of play in the slot should warrant him a spot into the preseason.