SAN FRANCISCO -- Forget about the struggle for eyeballs, or mindshare. The real body-part battleground these days is your wrist.The past year has seen an explosion in wearable devices designed to monitor your activities and sleep, and urge you on to healthier habits: the Jawbone UP, Nike+ FuelBand and Larklife, to name three recent examples.Now a new entrant in the sweepstakes has upped the ante. It's the Basis B1, a band that tracks everything the others do, tracks some things they don't and tells time, too.Most activity trackers are built around a motion sensor called an accelerometer, the same thing that detects when you turn your smartphone sideways. In a fitness band, it can measure things like the number of steps and, through body movements, how long and how deeply you sleep.The Basis, which costs $199, has one of those. But it also has other sensors on the back of the watch to monitor your heart rate, perspiration and skin temperature throughout the day and night, allowing for more detailed data.The information is combined with an easy-to-use website and soon, the company promises, mobile apps to provide tracking and continuous encouragement.While the Basis won't be mistaken for a fashion statement, it isn't much more obtrusive than a conventional digital watch. The sensor module is black, but it comes in a choice of black or white wristbands, and is light enough to be worn comfortably day and night. (The company has plans for more stylish bands a bit down the road.)Since it's water-resistant, you can wear it in the shower or when washing dishes. About the only times it needs to come off are when you're swimming or using the included proprietary bracket that connects to a Windows PC or Mac USB port to upload data and charge the watch.While you'll get the most out of the band if you sync and recharge it once a day, the company says a charge will last four days, and the device can store up to seven days of data.The gamelike website is integral to the device. Through it, you establish healthy targets that, as you achieve them, award you points that you use to unlock ever-more challenging goals.Basis started me out with the lowest of goals, awarding me points simply for keeping the watch on. I then set up a few myself: taking at least 6,000 steps a day, for one, and trying to adopt a consistent, reasonable bedtime, for another. (No more 11 p.m. Seinfeld reruns.)As I began to meet those targets, I was able to establish additional ones: moving around more during the day, burning more calories and the like. Tapping the watch's screen gave me real-time updates on how I was doing.I also learned I get more sleep than I thought -- perhaps because the Basis, unlike competing devices, is smart enough to sense when I doze off and doesn't have to be manually set in a sleep mode.Though I generally found the watch a welcome companion, the screen could be hard to read when I just wanted a quick glance at the time.And it lacks the silent-alarm feature found on the Jawbone UP and Larklife, among others, that awakens you by vibrating without rousing a still-sleeping partner.I also sometimes received error messages when I attempted to upload data from the watch, even though the transfer was successful. (The error messages appeared in both the Windows and Mac versions of the software.)The market for wearable technology is just getting started. There will be more wellness gadgets, smartphone companions like the much-buzzed-about Pebble watch and, if you believe the speculation, even a new Apple device, all competing for wrist space.Good thing we've got two of them.