Phone Creeper V0.9 (BETA) for Windows Mobile Cell Phones - "This is a phone espionage suite. It can be silently installed by just inserting an SD card with the files below on it. The program does not show up under installed programs or running programs and allows for a useful array or features. Phones running this software can be remotely controlled by SMS text messages. All commands will be silently received and deleted immediately and results will be issued back to sender. Pre-configured settings can be added to the installer to have your own default password and phone number to receive live updates. By default, this program will silently reinstall itself even after a hard reset, if the memory card with these files is still in the device." (more)
P.S. There is even an Anti-Creeper app. Both are FREE but donations are solicited.