We don't currently let you check in or check out guests, and we've been toying with the best way to implement this, and how to show you at a glance who has checked in and who has checked out.
We figured that, actually, it isn't so much about seeing who has checked in or not, but really about who is arriving today and hasn't checked in; and who is leaving today and hasn't checked out.
So we might do something like this:
Where a red border is people arriving today (27th July in the mockup) who haven't yet checked in. And yellow border is people who should be leaving today but haven't yet checked out. So if you have a yellow-bordered booking for a guest who should have left a couple of days ago, you know you need to go look for them under the bed...
Almost the opposite of how this information might normally be displayed, but we think this does a better job of giving you the information you really need than simply showing a "checked in" icon on the booking.
What do you think?