I just recently finished my Windows Phone Tivo app, called Tivo Command. Its free, and I'd love it if you could give ot a spin and give me some feedback. You can see it in the Market Place, just search for Tivo Command.
Also, I'm planning on speech enabling it using the new speech APIs on Windows Phone 8. (Full disclosure, I work at Microsoft, and I'm in the speech team, the same team that also speech enabled the Phone itself, Xbox/Kinect, and many other Microsoft products).
If you'd like to be able to talk to your Tivo, reply in this thread with what you'd like to be able to say, and I'll try to include that in the Windows Phone 8 updated version of Tivo Command later this month.
Let me know!