I've recently re-released an iPhone app called "TV Plus". Previously this was a remote record app for Sky, but is now a remote control for WiFi connected TiVo and Sky+ boxes.
Rather than the tradition grid-based EPG with 7-days of data, the app just shows what's on now, ordered by programme start time. It needs to be able to connect to your TiVo over WiFi (so, I think this means an ethernet cable from the TiVo to your home wireless router). Once connected, the app will change channel for you.
It's a free download for iPhone:
http://appstore.com/tvplus
Having very little experience of the Virgin Media TiVo world, I'd love to know what you guys think of it or if you have any problems using it, suggestions, etc.