I think this is the best heart rate monitor (HRM) I have had. I've had a couple of dumb ANT+ monitors and previously my favorite was the Wahoo TICKR X.
It connects to my ANT+ Power Meter, cadence sensor, speed sensor and foot pod. It then combines them with your heart rate into a single bluetooth stream. I use this with Sufferfest, although I believe Zwift works too. TrainerRoad does not currently, but I believe this is because they don't like multiple features in one bluetooth stream & not this device. If you have a different device I'd check with 4iiii or the device/App market if it works. Oh, just remembered; wahoo fitness app can see the different sensors too.
Once the sensors are paired with this device you don't need a phone for exercising. I ride on rollers to Sufferfest videos. This device means I only need to strap on this one device and the iPad doesn't need a dongle.
I haven't tried swimming yet. One of the complications Polar mention on their devices is water short circuiting between the two attachment points (polar make HRM for swimming that can use their Soft Strap) and the newish Garmin-swim HRM do not have connections at the front.... The Polar Soft Strap have rubber bits around the connectors that can be sand papered down to fit this and electrically isolate the two connectors. I have also used tent waterproofing silicone in the centre to stop that possible conduction pathway too. I am confident this will work, but will update this review. There is nothing special about the strap that comes with this device. It is standard. The good stuff is in the brains bit.
Incidentally, if you wake up this device it works as a bridge even if you don't use it as a HRM. Also it emits heart rate in both Bluetooth and ANT+.
The TICKR X is better in two ways: 1) led on front, but that is hard to see when wearing anyway. 2) they use the movement sensor to sense taps/movement. This device also has a sensor: hopefully they will add at-least some of these functions too.
I bought the heart rate metter a few months ago to use it with my garmin 910xt and my polar v800 and I'm very pleased with it. It works perfect with both. you need to configure it with the android app at first time but after you don't need to use the app at any time unless you want to pair a new device. It is really accurate. The only problem I see is I cannot use it whe swimming because the polar doesn't recognize it, but in this case I keep using the polar HRM.
This product worked perfectly for 4 months until the battery died (33hrs use according to strava), despite claims it would last much longer than that. After changing the battery, it worked for a week but the seal failed despite following instructions ensuring the seal was not damaged in any way. As a result the connections inside got wet and it is irreparably damaged. A bit worrying that it should fail so easily as a battery with corrosion can blow up when it causes a short circuit and this thing is right next to your heart.
I did receive a replacement from the seller following my original review and that worked fine until a week ago. I replaced the battery again following it dropping out whilst doing exercise and exactly the same has happened - the seal failed again and sweat penetrated the unit again. I followed the instructions to the T for battery replacement but it appears that the unit is only good for one battery and then you may as well throw it away because it lets water in and the fragile circuit-board inside doesn't like water.
I think it this would be a really a great product (5 star worthy) if only it could last for longer than one battery but sadly it can't. The 2 units I have received have lasted a total of 1yr and 10 months so unless you fancy paying ~£80 a year for a heart rate monitor then do not buy this product it.
Luckily for me the replacement I received came at just the cost of sending the original faulty one back to the US but since that has now failed too I will be looking elsewhere for a more reliable product in future.
Pros - works well on Bluetooth and ANT+ devices - CR2032 battery lasts quite a long time (over a 100hrs) - lightweight
Cons - HR sensors sometimes drop out when leaning on the top of the bars on the bike (upright riding as opposed to on the drops) - Changing the battery seems to break the seal irreparably and allows water into the unit rendering it useless from then on