If I had my legal 'druthers, such, er, "brain-derived mental content" would be flatly illegal to obtain without a specific and discrete sharing decision by the person, and such decisions may not be part of any contract, so:

1. You can buy a tool and use it to monitor yourself, whether daily-logger, dream-recorder, a fetish-detector, whatever.

2. You can share specific results with others on a case-by-case basis, but it's illegal for them to obtain it any other way.

3. It is not illegal (or at least unenforceable) for someone to require you to share results in exchange for something else, like requiring employees to wear a disloyalty-detector headband.

The question of how it applies to the 5th amendment right against self-incrimination... Hmm. Someone placing Guilt-O-Meter on your head would be illegal, but if you did it yourself and left log files around...