Jawbone's UP is back for 2012, and like that gym membership you signed up for and only used once, it's begging you to give it a second chance. The original UP launched last year to rave reviews, but the shine quickly faded as owners struggled with batteries that refused to charge and hardware that would unexpectedly stop working. Jawbone dragged it back into the lab and returned with a new version, all-change in hardware and software, and the subject of near 3m hours of testing. The wearable tracking market hasn't stood still in the meantime, however, so can the UP regain its lost momentum? Read on for our full review.