Then go back and do it again, but this time play black-hat hacker. Get creative rather than methodical. Try sql statements everywhere that might touch a database. Hammer every communication method it uses with denial of service abuse and then crafty mis-information that only you know enough to design.
The point is, make a game of it and you'll enjoy it. You could always trade code with a co-worker and keep score of how many bugs you each find in eachother's code.
I think I'll go polish my tinfoil hat.
The extender connects to the phone network via ethernet. If your connection comes via WiFi, then a nearby rogue AP could hijack it and sniff the traffic.
The picocell connects to sprint via ethernet. If you are doing that wirelessly, then it might be hijacked.
It is easier to write an incorrect program than understand a correct one.