You can use the Iris Keypad from Lowes. They are selling them for $29.99 this 4th of July weekend. You will need to read this thread to set it up.
Use the API to enter your Device Handler, FInd your new thing, then copy the code for the SmartApp usign the API, then finally go to makretplace to find “MyAPPS” and configure your Smart APP key code for arming and disarming.