In the latest issue of Popular Science is a report on a toaster-sized, battery powered device that allows the wearer to ascend at app. 10ft per second. The MIT students who invented it have already received some inquiries from canopy researchers. I thought it would be a good tool for rescue purposes. Sorry the article is not available online as far as I can tell, but here is another site on the invention:
http://tinyurl.com/2fnc5f