I have a hard time imagining being motivated more by health than longevity -- I would don a cyber-suit that keeps me alive but elderly for a hundred years to be rejuvenated later.
The way we (people in general) use the word "health" is based on a concept of the body as a well-defined entity. It becomes less well-defined when there is a technological solution that is as unobtrusive to use as part of your natural body; for example, a tooth with a filling works pretty much just as well as one that never had a cavity to begin with, so we don't think of it as an ongoing medical problem.
Givewell’s Holden Karnofsky, who has previously posted his thoughts on Givewell supporting SI/MIRI recently discussed the potential for Givewell to begin evaluating biomedical charities, in Givewell’s Yahoo Group. Someone suggested (as I have through less direct means) that they take a hard look at SENS Research Foundation, and then Aubrey de Grey appeared and began an interesting discussion with Holden.
The thread begins with Holden’s long initial post about Givewell’s stance on investigating and recommending biomedical charities, which is definitely worth the read for greater insight. The rest of the conversation is aggregated below for anyone else who can’t stomach Yahoo Groups’ interface.
Overall, Holden seems to agree with the goal of SENS, and interested in the details, but the conversation seems to have ended in October 2012 with Holden stating that he was waiting for Dario Amodei’s thoughts on SENS.