For anyone near a Warby Parker, they'll happily measure your PD in about 30 seconds. Measurements can vary slightly so you might want to do it a few times and average them.
You can also do it online with Warby Parker as long as you have a credit card (to hold under your face; not to pay with).
Now that is a clever way of doing it!
do they also need the picture of the backside and home zipcode?
if not, sounds like a startup idea.
The PD also varies a bit from reading glasses to distance glasses. If you are ordering single vision glasses, you might want to collect both numbers.