There are many inexpensive devices that will transmit audio from a remote target location to you, as you remain nestled safely in your special spying spot.
They work in the same way as a baby monitoring device, but can be concealed in much more cunning ways (though you can find instructions on how to “hack” a baby monitor, which is a powerful audio transmitter, to quite effectively work as a concealed spy gadget). Wall Plug Transmitters Audio transmitter bugs come in all shapes and sizes and can be planted just about anywhere (a private investigator from San Francisco named Hal Lipset gained fame in the 1960s after successfully concealing a listening bug in a Martini olive!).
Some of the least expensive and most effective transmitters are available to you in the form a wall plugs and outlets. These devices are perfectly disguised and will clearly convey all conversation and sound from a 20ft square room. There are several variations as well, including plug adaptors and power strips that all would need to be disassembled in order to be detected.
There is, for example, a wall outlet transmitter that can be installed directly into the wall. Its advantage is that, because it is placed directly into the wall as a standard outlet, it is able to have a 3-foot long antenna that can be concealed by tacking it up inside the wall itself.
This device has a substantially greater range (over 1500ft), but of course is a bit trickier to install. In addition to wall plugs and outlets, you can find other devices that will perform the same function, such as a popular lamp audio transmitter that can be set to transmit only when the light is turned on. Most of these devices retail between $60 and $100.
It helps to bear in mind that if you are in the least bit technically inclined, you may want to consider putting together some of these devices on your own (the same might apply to you if you are on a super tight budget and have no other option!). For example, an audio transmitter bug that will retail for $100 can be assembled using electronics parts from a local store that cost under $5 in total.
With these bits, a few parts from a broken transistor radio, enough patience to wind a wire around a bolt, and a battery source to power it all you’ve got enough to get you going. Many schematics for assembly of such devices are available online, but perhaps the most reliable book on the topic is Brad Graham and Kathy McGowan’s 101 Spy Gadgets for the Evil Genius (McGraw Hill 2006).