You've already got one. It's called your brain, and the connection is your eyes.
Seriously, did you read Karen's post? You can go into a store and pick up two identical packages of the same product, but if one came in last week's shipment and the other in this week's, the ingredients might be different. Companies change their "recipes" all the time, depending on price and availability of ingredients. That's why it is vital that we read the ingredients on every package, every time.