Ekahau Sidekick is a device that can be used for site surveying and troubleshooting Wi-Fi networks. Its on-board battery and CPU helps offloading much of the processing from the survey device.
The battery can last up to 8 hours without charging. The device is really light weight and easy to carry which also greatly improves surveying productivity. If you are looking for an alternative to a basic usb dongle, Ekahau Sidekick could be a perfect choice.