The BT-77 bluetooth gps receiver is very popular, I would consider it one of the most popular gps receivers. This is because it has been sold under different names including itrex, avl and other names

The bt77 uses a nemerix chipset, it is a 16 channel GPS tracking up to 16 satellites. Once fully charged it can last up to 30 hours. The box contents include the gps receiver and battery, an ac charger , usb car charger , a usb cable  and a cd. It may also come with a dashboard mat to place the receiver on so t doesn’t slide around. Because it comes with a usb cable , it can also be charged from a pc.

The device itself measures 81mm by 44mm by 20 mm. It has 2 flashing lights, a blue and red one,  the red light flashes when it has locked on to enough satellites otherwise it is steady. The blue one has to do with Bluetooth functionality.

With regards to performance, this isn’t a sirf 3 gps receiver but it comes close. The initial time to fix is less than 5 minutes, after that it takes 1-2 minutes and in most cases less than a minutes to acquire satellites.  I made comparisons between this and a sirf 3 gps receiver and this picked up 3 satellites in the middle of my living room while the sirf 3 one was fluctuating between 3 and 4.  Outside it was locking on to 5 to 8 satellites and it worked effortlessly from the car glove compartment.

The bt77  is an exceptional value for me because it is now very cheap considering it’s performance. It can be bought of ebay for less than £50 including postage.  It is really worth checking out.