I have tried 'Absolute Pitch Power'. Yeah it really works. The trick is to have the discipline (and time) to be able to do it every day for 50 days. It uses neuro-linguistic programming and is really trippy, but it works.
Essentially the course takes you through a journey, that you design yourself. For each note you make up a situation, location, colour, taste, smell, emotion, sensation and actively imagine this location and all other sensations while listening to the note in different octaves and on different instruments. You also have your screen flashing in that notes colour at an Alpha-state strobe.
Essentially you are hypnotising yourself with triggers. Hence after a while you hear the note, say C, and you immediately are transported to your location for that note, see the colour etc etc and hence can identify the note. After a while of this apparently, I didn't get this far, you just know which note it is automatically without all the sensory stuff.
While I was doing the course I used real sensory input where possible.
So for 'D' - I was sitting infront of my screen, in a relaxed state, the screen flashing yellow at an alpha-state rate, I was imagining being at a beach I know, the yellow sun beating down, the sand, the grass roofs all yellow. Actually eating Lemon sorbet and sniffing citronella, I imagined the feeling of the sand in my hands and the heat of the sun etc etc. I did exactly the same process each day I reviewed 'D'. Sure enough when I imagine that environment now, I can hum a 'D'.
I only did C, D, E, F (you don't want to know what I was imagining for 'F', well at least it can't be written here

.
I really want to get back into it. If you stop for a couple of days its hard to go back.
Cheers,
Alan