Hi Michael
See: http://www.utasker.com/kinetis/LLWU.html
Then see http://www.utasker.com/kinetis/FRDM-K22F.html which allows you to choose any LLWU mode and wake up from it using a push button (either temporarily to do one operation or permenently to RUN mode, or from a RTC alarm).
If you need an immediate and complete solution just take the uTasker project (it is bare-metal in the sense of your requirements) and includes complete power management support integrated with no more work (as well as almost everything else that the K22 could need, plus a K22 simulator that allows the complete project to be tested in (approx.) real-time, excercising peripherals, interrupt, DMA etc...).
Regards
Mark
Kinetis for professionals: http://www.utasker.com/kinetis.html