Automatic Lock-Boxes for Rentals

[Cassi Justiz]

Does anyone have recommendations on electronic lockboxes for self-showings? 

I've found a few online subscription services that allow for self-scheduling, but I don't want to do a subscription based product. I would rather just buy the lockbox, utilize the services that I already have in place for screening and send a one time (or changable) code to the prospect for self showings. 

Any suggestions?