I've managed to get into the EZ Rider pilot program, and am pleased with it.
This is a smart card that is auto-loaded with value from your credit card and only requires
being placed on the sensor pad on top of the fare gate for entry and exit.
I am aware that this means that I personally can be tracked on BART, and that this is not cutting edge technology, but it certainly is convenient. I also have an Oyster card, and have used that a fair amount.