According to the fine folks at MLBTR:
Simon posted a 4.90 ERA with 6.5 K/9, 3.1 BB/9 and a 43% ground ball rate in 115 2/3 innings as a starter and reliever for the Orioles last year. He has a 44.7% ground ball rate and an average fastball velocity of 94.5 mph in four seasons with Baltimore.
Ryan Madson will miss the 2012 season and Nick Masset will open the season on the disabled list, so the Reds are short on relievers. Simon will join right-handers Jose Arredondo, Logan Ondrusek and Sam LeCure in manager Dusty Baker's bullpen.