As you probably know, payment preimage possession can be used for proof of payment of a specific invoice. It is currently very difficult to do that manually with the tools available and it is not really usable for the end user.

Is there any wallet, service or tool that can verify that an invoice is paid by providing it the invoice and the preimage?

Are there any services that actually use the preimage proof? An example may be an automated delivery box. You pay for your product to be delivered and when it is you use the preimage to unlock the correct box? In this example my experience with such services (with fiat payment) is that you simply receive a pin code as an sms, but if hypothetically bitcoin is used as a payment, it would be cool to use the preimage itself. Maybe it can be presented as a qr code, or part of it (enough to guarantee that you didn't guess) entered manually...

What do you think?