I have been using MythTV as an open-source "Tivo" for years. In the last year or so, we've had a Nintendo Wii hooked up to the same TV, and I used the Wii remote to control MythTV.
One way to do this is with Benjie Gillam's MythPyWii. Used that successfully and was happy with it. Check it out if it fits your setup.
After a recent rebuild, I had issues getting MythPyWii to do what I wanted. Mainly, I was needing to run Mythwelcome (so that I could power down the box when it wasn't in use). To start up mythfrontend, you need to click on the button on the Mythwelcome screen. I couldn't find a way to do this with MythPyWii. Maybe there is one, but I didn't find it.
Enter XWii. Nice little program and lets you control your X-windows mouse from the Wii remote, regardless of program. This let me use MythTV and anything else (maybe the new Hulu desktop?).
There are provisions for creating your own profiles for different applications... here's the initial pass I came up with for Myth:
#MythTV
[a]KEYBOARD Return[/a] # ENTER
[up]KEYBOARD Up[/up]
[down]KEYBOARD Down[/down]
[left]KEYBOARD Left[/left]
[right]KEYBOARD Right[/right]
[minus]KEYBOARD d[/minus]
[plus]KEYBOARD p[/plus] # play
[home]KEYBOARD Escape[/home]
[1]KEYBOARD i[/1]
[2]KEYBOARD m[/2]
[b]MOUSECLICK 1[/b] # left click
[acc_mouse]1[/acc_mouse]
[flick]KEYBOARD z[/flick]