I have trained Mila to use a potty bell to indicate when she needs to go outside for “business”.
Find the dog trick tutorial here.

This is very useful, but also a little tricky. Because in the dog’s mind sometimes the bell mutates more into a butler bell – that’s when your dog starts training you. Don’t let her fool you into answering her ringing, when she is just seeking attention, because that could spark the bell to go off all the time.
Luckily over time I learned to tell, if she is ringing for “potty” or other things. In the video below you see Mila using her “potty bell” to tell me that she wants to GO … outside and play 🙂 If I smell the ruse and do not respond, this is what happens most of the time: