The 32-year-old didn't command a transfer fee with his contract coming to a close at Reading.
Redknapp told The News: "I've taken Glen Little from Reading and I think he could prove to be a surprise this season.
"If he can stay fit he has great ability and will cause sides problems.
"I think he can shock a few people and be a great free transfer.
"I've spoken to Stevie Coppell and he said if we don't want him to send him back to Reading.
"I think they were disappointed to lose him.
"They were desperate for him to stay, but he was out of contract.
"They were sorry to see him go. He can do things, though, and he can create goals.
"It is going to be interesting to see him play."