These Work Zone inspection cameras seem pretty handy little tools, these will be in Aldi from 25/08/13 for £69.99 which seems pretty reasonable.
Product Information :-
Find your way around air conditioning systems, boilers, inside walls, suspended floors and more.
Camera head with 4 x LED lights to illuminate objects
Waterproof, flexible gooseneck cable retains shape
Power supply: 6V DC
4 x AA batteries (included)
Camera diameter: 8mm
Includes: 2.4" TFT monitor, 3 retrieval tools and mirror attachment