To become a beta-tester, you watch the company websites. Some of 'em will post when a product opens for limited beta-testing.
As to reviews, if you want to do it for free, just contact an appropriate site owner, who may agree to publish what you've got after they've read and edited it. If you want to make money, forget it. The market is almost broken, now, due to the failure of the online web advertising model, and a lack of good print mags. That may change in the future, but right now, you'd have a better chance of selling New Age journals to Pat Robertson.