ALERT -- APR 2015 -- Bluetooth GPS devices stopped working under Apple's iOS 8.3. -- DO NOT USE WITH iOS 8.3 --UPDATE -- JUL 2015 -- Apple fixed the Bluetooth GPS problem in iOS 8.4. I confirmed the GLO works fine on both my iPad and iPhone under 8.4!UPDATE - MAR 2016 -- The GLO continues to work under iOS 9. I've tested it with iOS 9.02, 9.1, and 9.3 and found no issues.UPDATE - May 2017 -- Currently using under iOS 10.3.1. I originally bought the module to use with my WiFi-only iPad, but found today it can help my MapMyHike app on my iPhone 6 resolve my workout distances more accurately. The iPhone 6 (and most smartphones) use a hybrid GPS/Cell Phone Tower location system, which is not all that accurate for someone on foot. Added a picture to illustrate the accuracy increase on the iPhone.BACK TO THE ORIGINAL REVIEW:I bought my Garmin GLO over a year-and-a-half ago, so I have some experience. I use it with a WiFi-only iPad. The GLO is a small, long-lasting, accurate unit with fast updates and great coverage, but it lacks one simple item I think is very important: A battery level indicator in either hardware or software. The power light on the unit will blink about 20 minutes before the battery dies, but that's not enough, IMO. Luckily from my experience it appears you should be able to count on most of the 12 hours they predict, which should outlast most devices it gets paired with. Buy a spare battery for under $20 or an external battery pack, and you should easily get 24-hour coverage!Now, I've had some bumps along the road: The first unit I received stopped communicating after 3 weeks, and was replaced by the one that has lasted the last year-and-a-half. I'm hoping whatever made the first one stop communicating has since been fixed in production. I also had a recharge problem when connected to an external battery pack charger, but that turned out to be the charger (I thought it was the GLO for quite some time).Before writing this review I decided to test the discharge rate of the battery. Can it still last the stated 12 hours? The first test gave me 14 hours and 39 minutes of constant communication with a GPS app on my iPad, so yes! Pretty good for a year-and-a-half old battery. A retest the next day was within a minute: 14 hours and 38 minutes!I have seen zero compatibility issues with this device. It has worked with every map program and GPS utility I have thrown at it -- Apple and Google Maps, Google Earth, ALK Tech's CoPilot GPS, Waze, and MotionX's GPS Drive to name a few. I typically use ALK Tech's CoPilot GPS, because like MotionX's offering, they store maps right on the device so you don't need an Internet connection. Since I have a WiFi-only iPad, there is no Internet connection when I travel. It will even transparently Geotag my photographs! I do wish Garmin provided a utility that, besides showing the battery level I so desire, would also show standard GPS utility info like what satellites it is using, etc. Historically this type of utility has been a great troubleshooting aid.I answered a couple of these in the Q&A section, but here are some additional fixes & tidbits:1) DO NOT USE WITH iOS 8.3 (see ALERT, above).2) The power switch sensitivity you see in many reviews was fixed in firmware in late 2013. That firmware update was stable by early 2014, so all current production models should have it. Unfortunately I haven't been able to update mine. There seems to be a USB issue that is most commonly fixed by attempting the update on another computer. I only have one computer.3) The above firmware update also added support for up to 4 simultaneous Bluetooth connections, and gave the GLO the ability to turn off automatically after five minutes if there are no Bluetooth connections.4) The unit must be powered on to charge. Some people have dead battery issues because they do not realize that. Also, from my experience above, I would play it safe and recharge with a normal 1A power source, not an external battery pack charger. It should normally charge in a little over 3 hours from a normal 1A source, but from deep discharge it may take a while longer.5) You can geotag your photographs (embed the location where the picture was taken) on a WiFi-only iPad. Simply have the GLO turned on and connected when you take a picture (and have the option turned on under Privacy > Location Services > Camera!) Then you just need to carry the GLO in your pocket.6) Someone asked what version of Bluetooth it used, presumably so they could make sure they were compatible. I took mine apart, and it appears to have a Bluetooth 2.1 chip.Hope something here is useful to someone!