SmartDashboard.getX (getNumber, getBoolean, getString) are probably what you're looking for (it sounds like you already know about SendableChooser).
If you're using the default LabVIEW dashboard check out this doc:
http://wpilib.screenstepslive.com/s/...th-c-java-code
If you're using the SmartDashboard, you'll need to do a put of the key at some point (such as robotInit) to get it into the table. Then you can edit the value in the box on the SmartDashboard and do a get on the robot side (likely repeatedly in disabledPeriodic or teleopPeriodic).
Make sure to specify a default value when using the gets so your program still works if the SD is not connected.