Hi, pretty self explanatory. If wishlists don't already work in this way how could I set this up? Thanks.
Unfortunately it is not currently possible for wishlists when an item is re-stocked.
You can enable a reminder frequency field for customers wishlists which will send an automatic reminder email when the item is still in the customers wishlist and has not been purchased. If you want more information around this please contact support and they will help you enable it in your template code.
Obviously a customer can use the remind me feature on an out of stock product to be notified when an item is back in stock.