Bluetooth is today in a lot of devices and we don't even find that to be a special feature. Average USB Bluetooth adapters have a working distance of around 10 meters. Some low power devices may work on on even shorter distances. On the consumer market there is no need for very long distance Bluetooth communication (practical and security reasons). However there is an industry-type USB Bluetooth adapter that is easy to use and has much wider working distance - SENA Parani UD100.
This adapter can use an external antenna (RP-SMA connection) and thus work on on greater distances. With a Patch antennas the distance can reach up one kilometer in open space. With common dipole antennas (like those used for WiFi cards) the distance will be around few hundred meters. UD100 is Bluetooth 2.0 EDR device, so it offers (only) 3,1 Mb/s (0,38 MB/s) transfer rates. When connected to a computer working under Linux the device is ready to work without any additional steps.
We get a mini-antenna in the set, which is good only for short range operations. If you connect a 3-5 dBi dipole antenna the distance should be much bigger. The one kilometer is for patch antennas pointed at each other. When searching for phones and other Bluetooth devices the distance won't be as high as the second devices (like the phone) won't have a strong Bluetooth radio.
I got the UD100 to use for few days. I went to a local mall to test how good the range will be with better antenna. The test was quite basic - I just searched for Bluetooth devices for every adapter/configuration I tested. The results are as follow:
The chart presents the number of discovered Bluetooth devices for every configuration. I scanned twice allowing the adapter to pick additional devices (if they move in into the range or when some devices weren't added due to scanning time limit). Most of the discovered devices were phones, mostly Nokia. As you can see netbook Centrino Bluetooth adapter and UD100 on mini-antenna got very similar results. When I connected a 3 dBi dipole antenna the number of found devices was much bigger. It even detected one laptop, Officejet Pro 8500 a909g printer as well as few audio-visual devices ("video display and loudspeaker").
As you can see the UD100 is working as it should - giving much bigger working distance than average consumer devices.
Network hackers/admins/testers often use strong WiFi devices to test available wireless networks. UD100 would be the same thing for Bluetooth radio. Pwnie Express company created Pwn Pad - a customized Google Nexus 7 tablet running Android plus Ubuntu and packed with network hacking/analysis applications. The software and the tablet supports external WiFi, Ethernet and Bluetooth adapters sold with Pwn Pad. The Bluetooth adapter is the UD100.