Focus Peaking?

I am the original owner of a K20. I've enjoyed the quality of my photos immensely.

I recently received a K-01 that I planned on using primarily for Astrophotography. At $316.00 I just thought it would be worth checking out the techno improvements since the K20. It is so unique in form/shape and quality of images, I can't help loving it.

After attaching a couple of old manual lenses I'm blown away by the Focus Peaking method of focusing. So my question is, which previous and current Pentax SLR's have Focus Peaking in their feature set? Sorrry if this question has been asked to death, but I look forward to any dialogue on this subject.

Thanks, Robert