Back in the day, everyone had corded rotary phones. Now that you have moved to cordless or mobile, you can turn that old rotary dial phone into an interactive kid's toy.
Instructables explains how to add a Raspberry Pi to the rotary phone dialler. Each number on the phone can play a different MP3 file. Kids can listen to a different "caller" at each of the 10 locations. The tip suggests fairytale characters, but you can record anything you want.
If you'll be out of town for a while, leave a different message for your child at each location so they can hear Mum or Dad whenever they want. Check out the link for the full instructions.
Fairytale Phone [Instructables]