Recommendations for input circuitry

Hello, I am going to use the imp003 for a home automation project and have a few questions about the circuitry behind inputs. These inputs are dry-contact closures and analog 24VDC inputs. The 24VDC signals are commonly used for security/fire signals, and the dry-contact closures for simple wall switches.

I was thinking about using a voltage divider to reference the 24V to the imp 3.3v, then into one of its ADCs. I am curious if there are other way of implementing this, taking into consideration damage to the imp pins. I want to make sure that an average integrator (and their methods of installation) do not hurt the imp at all. My hope was to allow a single input to accommodate a dry contact closure or the 24VDC signal.