Would you like to test if your wireless device is actually transmitting, and at what level with which frequency? Then you need a spectrum analyzer like this one.
RF Explorer is a handheld digital spectrum analyzer and a very affordable tool for work in all ISM popular frequency bands. It is based on a highly integrated frequency synthesizer which offers high performance, compact size, low power consumption and low cost. It has been designed to be used equally well outdoor and indoor, and can be connected to a PC for extra functionality using standard mini-USB 2.0 connector.
This model has a wide band coverage to popular RF frequencies, starting at 15MHz and going up to 2.7GHz. This include very interesting frequency areas such as 2m HAM radio, all VHF and UHF, FM radio, GPS, WiFi and WiMax, Bluetooth, etc.
More information is available on the website of Seeed Studio and RF Explorer.