It really depends on how the technology is directed. If it's going to be used by the government and for storing personal identification material, it WILL be abused. Someone with a chip reader can just come by, tap you on your back, and bam steals all your personal info, copy it, install it in him/herself and parade around as you. Not good... However, for someone who can't communicate properly, is disabled, it might be valuable to them and help them if they get lost.
As for medical, scientific uses. It has great potential. It's already being used actually. There are swallowable cameras that take pictures of your GI tract and sends it to a computer wirelessly. Ear implants for those who lost their hearing (rather large currently). Any on the frontier there's neural implants that could potentially be used for controlling prosthetics with your mind, controlling seizures (actually I think this is already in use), real live telepathy!, receiving and sending information mentally in real time with computers, the implications are limitless. Imagine driving your car just by thinking, or special forces soldiers being able to communicate with each other and a commanding base without uttering a single word, or heck, seeing what the other soldiers are seeing, i.e. multi-presence.
Of course there's the darker side, where people can be kidnapped, their brains stolen, hooked up to computers and have to endlessly run factory processes, etc. Brain slavery. Or advertising companies injecting thoughts into you subconsciously by exploiting the neural transponders you have installed.