Undetectable? Loader No, Biosmod No. Ask someone to mod a copy of your bios, read more in the biosforum.
Here is a good breakdown dude. Loaders: Safe to use but can be broken easier Bios Mod: Can be risky when flashing but more solid, it can be detected as well but it is the best way to go as long as you accept the risk of potentially bricking your motherboard(Pretty rare). Hope that helps