Priiloader is a homebrew application which places itself before the system menu and patches the system menu to remove limitations and add a few things. Since its put before the system menu, it allows you to load into the homebrew channel directly. This allows you to repair your wii if you should ever brick, once the brick isn't a full brick.
Priiloader is perfectly safe. It take seconds to actually install, and provided you don't lost power during that, it won't brick you. Once you have it, provided your System Menu or System Menu IOS aren't deleted, you cannot be bricked. This means you are protected from Banner Bricks etc. Also, you can set Priiloader to autoboot BootMii/IOS, and have BootMii/IOS setup to load SNEEK, meaning you can boot directly into a SNEEK environment, i.e. it is IMPOSSIBLE to brick your Wii, as your real NAND isn't touched.
Note- If you followed Cile and/or Mauifrog's Softmod Guides you should already have Priiloader installed. You can check by pressing and holding the reset button when your Wii is booting.