If there was spyware written by someone else, it would need need to by signed to monitor secure applications. You would need to manually install the spyware application yourself. I suppose its feasible however unlikely.
I will write and sell you a program to detect Spyware on your BB. For free it will also detect viruses. All for the low, low price of $99.99 with free daily updates.
JUT KIDDING FOLKS.
Not even feasible - how are you going to get to the Address Book and mailer software. RIM has those APIs under wraps.