We have been using a wireless doorbell for different purposes in my classroom for nearly a decade. Our most common use is a way for staff to summon other staff to give assistance, for example we keep a wireless doorbell in the changing area so that when a student who requires two staff members for a transfer is being changed only one staff has to stay during the change and then she can ring the doorbell to call for someone to help with the transfer back to the wheelchair.
We also use a wireless doorbell as a way for students to call for assistance, placing the "ringer" on the tray of a special needs toilet seat and allowing a student privacy with the ability to ring the bell when finished. Another way we use battery operated wireless doorbells is for students to summon staff in the community, again with the ringer (adapted or unadapted) on the tray the student can "ring the bell" to let us know that he or she needs help. In a smaller store the receiver can be kept with the student and the staff can track down the student by listening for where the ringing comes from. In a larger store the student can use a code to indicate location. One ring is the front of the store, two the back, three by the restroom, etc.
Wireless doorbells will run you $12.00-$30.00 depending on features at your local hardware store and eBay and other websites sell a wide variety of novelty doorbells if you are looking to lighten things up. The "ringer" can easily be adapted by someone with basic soldering skills or Enabling Devices sells a pre-adapted wireless doorbell.
