Electric lock box for potential tenants

[Dave Kuether]

What does everyone use for a lockbox when they have potential tenants wanting to see the property? I am currently using a PM and will be self managing going forward soon.  I have seen some that use an app and a code that expires in a set amount of time that look great but are also expensive. Since you aren't there showing them the property, how do you validate they are who they say they are take credit card info before they get a code if you use the smart app lock box? If you don't use the smart lockbox, what do you use and are you there to show the home?