More useful surveillance information can come from:
your phone records, online activity, credit cards and financial info. All of which can be easily tracked. Plus there are a billion camera phones and digital cameras already.
Below are some sites for commercially available spy gear.
These are covert listening devices or detection devices. Professional grade gear can cost $10,000. More expensive gear has higher quality microphones, more channels for recording, a writable optical drive for the recordings etc...
Brick house security
Spy associates blog
Higher end audio surveillance gear is described
More from spy techs
Spy detection spy nyc
Satellite surveillance and the soon to be common gigapixel cameras
City wide blimp monitoring
Government monitoring of cities
Super high resolution Lidar