The thought is probably that since it is inside you it can't be stolen, so obviously it would be more secure than a form of ID that could be stolen. I think it's pointless, and actually potentially hazardous to the user:
- It would only last a few hours. It's powered by stomach acid, once it's out of the stomach it would stop working. What are going to do, take an authentication pill every day? Why not use other biometrics what rely on what you are, rather than what you have?
- It's dangerous to the user. Nowdays if a thief wants money out of your bank account he/she will skim your card and capture your pin with a camera or a fake keypad. It's not a violent crime. With an intestine-based authentication system (or any biometric authentication system) the thieves will need the user physically in order to authenticate, opening the user up to kidnap, coercion, forced vomiting, or at worst having their guts cut out
It's an interesting experiment, however I wouldn't actually want to use it. If someone threatens me with a knife or a gun wanting my money, entry into a facility or whatever then I can give them my cards, my codes, my key fob, whatever. The trouble with a swallowed device is that I can't give it to them at will.