His numbers this year are decent and hopefully he can help the pen. He was once a top 100 prospect. I don't see how this can hurt at this point anyway with our bullpen being as overused and bad as it's been lately.
Rotoworld says he has a live arm that can set up/eat innings in the pen. Low risk (e.g better than Remlinger), high reward.
Remember, Harville was one of the Astros pitchers involved in the no-hitter vs. the Yankees a couple of seasons ago