Open house sign in apps

I’d like to start using a open house sign in app on my iPad and don’t know which to use. Who else is using one? I’d like a recommendation. Also, is there one that integrates into the REW CRM?
Thanks!

@Morgan does REW integrate with Spacio?

We have done custom integrations with them in the past, but not since they were acquired. I am sure they are still amenable to it though.