He's small (5 10 1/2, 180 pounds) and fast (4.38 40).
He took an unusual path to the NFL: Intense football league, Arena League, Dolphins PS 2009, Skins PS 2009, Skins 2010-11.
He's surprisingly old for a guy who hasn't played much in the NFL, 29 years old, so he really isn't a developmental prospect.
It seems like he is a guy to fill a short-term hole with the loss of Miles and Otree. It is surprising that they think he is more ready to contribute on a fill-in role than Holmes considering he doesn't know our offense, doesn't have a lot of pro experience, isn't known for his routes or his hands.
My guess is Garrett really felt he needed a speed WR and he was the best one available on the street. I really can't see any other reason to bring him in.