Don't get too hung up on the terminology -- you call her a whore now, why not call her a prostitute? I don't think there's much difference between what the two of you do and what most couples do (exchanging gifts for favors), except that the two of you are a lot more honest about it than most couples.

Now, BACK TO THE ORIGINAL TOPIC, since you're seperated during the week, she could have to perform some daily task while you're apart. Two common-as-dirt examples would be: Having to write you a dirty story (in installments of so many words or so many k per night), then read it to you (maybe acting out the parts?) when you get together, and; having to masturbate for so many minutes per night without cuming. Five to fifteen is good -- you can refine it as you learn how effective (or not) this is with her. Maybe more minutes (or more pages) is worth more interest? If she's the exhibitionistic type, you could have her doing nude calisthenics, maybe with the drapes open, every night (half an hour -- she can do it while watching a favorite TV show).

Although it got considerably sidetracked, this was a good initial posting, and I commend you for inventing a really cool game.