Grayson Peddie was kind enough to write a how-to explaining how to connect your wireless doorbell to your M1. Eventho he used the Elk M1 in this how-to, the concept will work with other devices supporting analog inputs such as the ADI Ocelot. Visit the link below for more details.
How To Wire A Wireless Doorbell to Elk M1 Gold
How To Wire A Wireless Doorbell to Elk M1 Gold