Playing downloaded wii games

You can Play Wii backups without a mod-chip.

Using a LPT 25 way cable connected to the pc from on side and solder to the DVD drive firmware on the other side. (only 5 wires to be soldered). Your pc will then play to same role than a modchip. Remplacing on-the-fly the firmware restriction to accept burned disc to boot. A easy and cheap (3 $) mod.

Bye Bye Warranty?

Yep, but its a relatively easy and safe mod. Soldering points are quite big so even with a cheap solder iron and minimal skill shouldn't be a problem.