Depending on what model TiVO it is, you can also purchase a wireless networking adapter for it so it can use your existing wireless network and talk to the server directly instead of making phone calls.
Thanx
That only works for series 2 TiVo's, the DirecTiVo doesn't support WiFi.
DirecTV is in the process of phasing out their Tivo, it won't support their new HD line-up for example.