You can open the Sharebox remotely from wherever you want. Just make sure that the person retrieving the item is in front of the box. We wouldn't want you to lose your stored content.
Open the Sharebox App
Select the reservation you have shared
Make an appointment with the one you've shared with to be at the right location- in front of the Sharebox
Then you can open the box - remotely for the one you've shared with.