Choosing the right brainwave tracking device for meditation

Hi,

How many of us use brainwave tracking devices to keep track of our meditations? I always wanted to gauge the level of meditative states I can reach. There seem to be so many devices and hardly proper comparison of the various devices. I'd like some suggestions, but no links please, just the name. I would like to have a brainwear that has gamma, beta, alpha, theta, and delta ranges support. So, what do you use? Which device has options of tracking exact brainwaves than general focus and attention etc..