well, i have save manager GX and it hasn't done anything to my wii. But if you really want to install it, you always want to make sure that you have bootmii (or some kind of back up program on), it gives you the option of loading directly to the homebrew channel when you turn on your wii, so if you minorly brick it you still have a chance to save it. (pending on what you did to it, anyway) remember, you don't have to get it... so get at your own risk if the site says it's not safe. Also, don't do it if you don't feel comfortable doing it, it probably won't end well D:
Thanks i'll do that for back up
It's not a dangerous app, the warning is there because it changes your Wii's NAND, which is in fact the internal memory. Because the app only affects your savegames (stored in the Wii's memory), it will never brick your Wii. The worst thing that could happen is corrupted savefiles. But like Yoshi said, it's never a bad thing to have some form of brick protection
Oh so that is the warning for that's good news then thank you