Mobile cell phone interceptors and scanners will allow you to intercept and record (if you buy a separate recorder) mobile phone conversations automatically, at the push of a button or you can program it to intercept pre-determined numbers.
What you use it for is up to you, but please note that listening in on someone else's conversation could be illegal in your country ...therefore, please make sure that you adhere to the laws.
Most countries have tough laws against eavesdropping; so you could get into trouble if you are not authorized to use it.
Scanning and intercepting cell phone conversations require the use of specialized equipment and the top of the range interceptors are usually sold only to government agencies.
They are extremely expensive ($300 000+), but they are also the best and highly sophisticated.
The scanners and interceptor described on this page are much more affordable, especially if you only plan to use it a few times.
Both models have the ability to intercept and record (you can attach them to any tape or digital voice recorders) cellular conversations, but the AU 206 only allows random scanning of phone numbers. (AU 206 intercepting range = 5 miles).
It's cheaper than the Au 208 interceptor but you have no control over who you want to listen to.
The AU 208 interceptor allows you to store up to 20 numbers, which will automatically intercept both sides of the conversation once the specific number is activated. (Intercepting range = 10 miles).
Mobile cell phone interceptors like the Au 208 make use an A and B system that defines the regions where this interceptor can be used.
An alternative to a cell phone scanner is to make use of cell phone spy software . It works on almost any mobile phone... you will be able to monitor calls as well as different types of text messages and voice mail.
Once again, if you use cell phone scanners, mobile cell phone interceptors or any other listening devices, please make sure that you stay within the law.
Interesting question. Can law enforcement scanners pick up mobile phones?