Kernel Manager helps you locate alternate kernels that can overclock or undervolt the CPU, or do some other interesting things.
The Lite version disabled the "filter" menu which helps you narrow down the choices, like "all the kernels that can do at least 1 GHz" and so on.
Your phone needs to be rooted first.
The app also incorporates ratings for features and stability, among other publisher provided information. As the kernel list is dependent on the kernel writer himself to provide, this can lead to extreme slowness.
I tried to flash one of the kernels and the app just FC'ed after getting root permission. In other words, it didn't do anything.
Rating: Try it (or just skip it, if you already have ROM Manager)