How to prevent sealed in product battery drain on store shelf?
If your product has a microcontroller which consumes tolerable amounts of current in sleep mode, you could simply wake up every minute (or whatever interval is appropriate) and check if the box is open using whatever sensors you like (Hall for magnetic field, photoresistor for light, etc). The check can take very little time, and if it's negative you'd go back to sleep for another minute.

For example, drawing 6 mA for 1 ms every minute produces the average current of 100 nA. Assuming a current consumption of 500 nA in sleep mode, you'll have a total average discharge current of 600 nA. You'll have to find a compromise between battery shelf life, wake-up delay and the appetite for current of the sensors which tell you to wake up.