If you set configuration to "Notify Me" on any product - it has a little note on the front page - I fill in the note and it gets stored in the Product >>product status area.
I can see it there and it is stored along with a few other people who want that product - the settings shown in the image suggest send to a number? The number represents How may customers?, or customer 1 or 2nd or 3rd . If it is customer number 1 then there needs to be a number in the setting as shown. I presume that you might have a special customer that you want to pick first to tell and he is number 5 customer - maybe the list needs a set number next to him/her. But it does work and I like it.
[attachment cleanup by admin]
Hi
The email is sent to the X first customers that is waiting.
A good idea for the future, will be to have the choice to prioritize customer rather than non customer.
If you want to prioritize a specific customer, then you can send him a private email, or an email via the order.