We've seen keys being replaced by key cards, new LCD TVs, WiFi and LAN in each room but the one thing that doesn't seem to have changed is the "Do Not Disturb" tag that can be hung on the doorknob outside the room.
In the majority of hotels I stayed, this tag was also a "Please Clean the Room" sign when turned over. These two use cases are obviously diametrically opposed to each other and it is very easy to select the wrong one. You also can't be sure that some passerby just turns the tag.
The "good" ones make turning difficult, the bad ones hang on a string and can be turned by e.g. the draught of a closing door (see image below). In very rare occasions - at least here in Europe - a hotel offers two tags, one for each use case. This seems to be the best approach so far, as this eliminates the possibility of accidentally selecting the wrong use case. But it still doesn't prevent from stealing or removing the tag.
My question: How can these simple use cases be improved for the user (i.e. hotel guest) given the following restrictions:
- solves all of the problems mentioned above (easily used wrongly, easily stolen/abused)
- does not cost a fortune (must be possible for a hotel to easily apply to each room)
- most importantly: doesn't require a user manual, i.e. instantly (more or less) clear to the user and
- does not need a new convention to learn (a new convention is e.g. "All rooms are DND by default unless a sock hangs on the doorknob")