There is a lot good about the Slice. I think the basic idea is sound - steps are very superficial and don't really measure anything. Heart rate is a much better indicator if you want to measure exercise. The device is generally OK - it's reasonably comfortable. It is able to read your heart rate. It sends the data to your phone, where an app gives you a score. But there is a lot of detail in making that practical. It seems like everything nowadays is run like a kickstarter project - get something out the door, then work out the details later. The Slice seems to follow this pattern. For example: - why is the button so huge? You'd think from the shape that it is a rocker switch, but it isn't. Because it's so huge, if your press is a little offset from the center, it will click when pressed, but nothing happens. That big ridge on the button that seems to be saying "press me here" is a decoy. If you press there, nothing happens. It's really annoying to figure that out in the first minute or two of use during pairing and firmware update. - the firmware update is glitchy. The first unit I had bricked itself during firmware update. The second one failed during the first attempt, but succeeded on the second try. Yes, firmware update is hard. But it needs to be reliable if you're going to let devices out with old firmware so that firmware update is 2nd thing the user has to do when setting up the device. - the app is so minimally featured that it's more like a proof of concept than an actual fitness application. It collects the data in a highly compressed bar chart which would be cool as an overview - but that's it. You get your magic PAI score, but no real view of the data. It's not clear whether the data stays entirely on the phone. During sync with the device it says, "syncing with server", but you have no visibility into that. It might be cool from a privacy perspective if the data stayed only on the phone, but there's no way I can find to access the data. You can't export it to the Apple Health Kit, or upload it anywhere (e.g., the way Garmin devices work with the Garmin Connect web site). As far as I can tell, your data is dead-ended in this app, and there is no way to get it out, or back it up. - the PAI score seems like a really good idea. Steps are superficial as a metric, and those other trackers can't even count that accurately. But the PAI score seems somewhat arbitrary. For example, I get 25 points for walking around in the grocery store for 30 minutes. 50 points for inline speed skating 18 miles in a little over an hour. I understand the points are just an arbitrary number. It's all just for motivation anyway. But the points need to make just a little bit of sense, otherwise it's not motivating. When the points don't make sense, you feel like you're being cheated out of something. Maybe the points will level out over time with more use. - Sleep tracking is pretty much non-existent. It gives you a highly compressed chart similar to the one for workouts, with light sleep, deep sleep, and awake totals. It seems like the HR display uses your "resting heart rate" as the minimum value, and won't show anything below that. That's a bad idea, because nighttime heart rate often goes well below that. There's a well known dip upon going to sleep, which is part of the HR you want to see for sleep tracking, but the chart cuts that off. This is just plain dumb. The chart floor should be the lowest data value, not "resting heart rate". [update: It seems like the device keeps updating resting heart rate over time to the lowest value it has observed (though it's hard to tell, because you can't readily confirm any minimum value). This is a bad idea because "resting heart rate" normally refers to your awake daytime minimum. The nighttime minimum can be considerably lower than that, but you don't want to treat that as "resting heart rate" for exercise purposes.] - I'm getting about one day of use out of it between charges. I've subsequently turned off all vibration and notifications, and will try never activating the display to see if I can get two days out of it. [update: after turning all the buzzing and alerting off, and not fiddling with it unnecessarily, I burned 20% of the charge over a day, so you should be able to get 4-5 days of use with minimal use. Probably 1 day if you turn all the alerting features on.] - The physical unit seems solid and comfortable. After 3 months use, the screen is still unscratched, although I've accidentally bonked it a few times. It's pretty comfortable, pretty much like it's not even there. The strap and the unit itself seem to be holding up perfectly. I get it wet almost daily, and no issues so far. One Month Update: after a month of use, I'm still running PAI scores around 230-280. Supposedly, it adapts to your level of fitness, so that 100 becomes the right number for you, and it becomes harder to rack up big PAI scores. So far, I'm not seeing that. Wearing it has become fairly ordinary. I hardly notice it anymore. Three Month Update: about once every 2-3 weeks, the phone app hangs on the purple "Syncing with Server" screen, and then crashes. After that happens, it won't do anything except show that screen, then crash. The only way I've found to get around this is to delete the app and re-install it. Then you lose at least some of your data. This is fairly annoying. Hopefully it will be fixed soon. In Summary: If you want all-day HR tracking, this seems to be the way to go. But there is a lot of room for improvement. Hopefully there will be future updates to the PAI app that let the data out of jail, and make it more generally useful.