After testing all the pieces of a tiny pill-size device, Albert Swiston sent it on a unique journey: through the guts of six live Yorkshire pigs. Pig bodies are a lot like human bodies, and Swiston wanted to know whether the device would be able to monitor vital signs from inside a body. It did. It’s the latest in a small but growing group of devices that soldiers, athletes, astronauts and colonoscopy patients have gulped…