here are some of the simple electronics that I use. key word here also being cheap. I use these together and by themselves depending on what I am doing.

cell/camera phone, a must have these days, also use an ear bud for hands free rather than bluetooth. bluetooth can be hacked in seconds. video camera for better video than a phone, such as proper surveilence. downloads as a extra drive via USB, keychain/spy camera for being sneaky. am/fm reciever to get weather reports or traffic info. walkie-talkies for keeping in touch with a spotter or helper. (or sidekick)
GPS because they all have the feature for current location wich will show the address and street. great for laneways or where numbers are nowhere to be found.
cheap lasers can distract, blind and startle. most people when they see the red dot on their chest think GUN before anything else. kinda a dirty trick but oh well.
also the thumb drive because you may find you get the chance to raid a criminal's computer. dont think it cant happen. I had the chance but no drive to download to.
these are some of the tools you need to keep in mind if you pan on fighting crime these days. eyes and ears are more welcome than fist and boots.