1st is a backup cam or sensors for a h3.
2nd is a bug gaurd.
3rd is why does my h3 idle rough at any temp. with no check engine lights or codes showing on the diag at the dealor?

 

Here's the answer to you first question:

http://www.amazon.com/Backstopper-Co...;s=electronics

As for the second question....no idea.

Third question. Sounds like your idle just needs to be adjusted. Take it in to your local Hummer Dealer and have the service department take a look at it.