It's a problem in quantum mechanics as well as fitness tracking: Getting measurements off of a moving body is tough. I'll leave the former to Heisenberg. In terms of the latter, heart rate monitors are a prime example. The latest tech is portable and wireless - it employs photoplethysmography (PPG), in which light is used to take measurements of the volume of blood moving through your skin. This volume pulses with each heartbeat, so by tracking those pulses, the monitor tracks your overall heart rate. But these electro-optical sensors are delicate. The movement of your skin and muscles during a heavy workout can throw the sensors off - and aren't heavy workouts when we could use heart data the most?
MIO Global, a fitness watch and pedometer company that's been in the game since 1999, set out to find a solution, and they came up with the Alpha. This heart rate monitor watch pairs PPG (in the form of two green LEDs and an electro-optical cell that sit on the underside of the watch head, against the skin of your arm) with a separate motion sensor to measure your body's movement. Software in the watch parses information from both sensors to provide a live, continual stream of motion-corrected heart rate data.
You can read that data on the Alpha's non-backlit LCD display, and, if you'd like to save it for perusal later, you can sync the watch to a fitness tracking app on a mobile device with Bluetooth 4.0 during your workout. (The data is live only - the watch doesn't store anything other than a brief overview of your most recent exercise session - so you have to bring your mobile device with you.) As of this post, MIO has no such app of its own, but its Web site lists Runkeeper, Mapmyrun/Mapmyride, Strava, Wahoo, miCoach, and Endomondo as being compatible.
The Alpha should hypothetically work with any app written to communicate via Bluetooth 4.0, but keep in mind that 4.0 is a relatively new protocol, so not all apps are written for it - and not all smartphones and other devices come equipped with it. (The iPhone 4s and 5 do, and a quick Internet search or flip through the manual will let you know about your Android or Windows 8 device.) MIO funded production of the Alpha through Kickstarter, and they offered those early adopters an ANT+ version as well, but so far only the Bluetooth version has made it to production.
But all that technical stuff aside: the, ahem, heart of this watch is its pulse monitoring and alarm system. Before your first exercise session, you input your upper and lower heart rate limits, plus your target heart rate zone, into the watch. (Learn how to determine those here.) You can then set the watch to alert you with a beep and color-coded LEDs on the face of the watch (blue = low, green = on target, red = too fast) when you stray out of your target zone. Staying within this range while you're exercising helps ensure that you're getting something out of the workout without straining yourself. Even without syncing the watch to an app, reliable access to that data alone will make the Alpha worthwhile for some fitness enthusiasts.
The Alpha is currently being sold on MIO's site for $199 to the U.S. and Canada only, with hopes to open shipping worldwide soon. If you're undecided, I highly recommend checking out this thorough review by DC Rainmaker to suss out whether it's right for you.