Question:
What is the proper type smoke/heat detector to install in a garage and kitchen to hook to my omni pro 2?

Answer: -None. It's a code violation (not to mention bad practice) to install smokes in garages, kitchens, laundry rooms, etc., because they will false alarm due to normal conditions (cooking, car starting, water vapor) in those rooms.

-I can't imagine a code violation for a smoke detector installed in a location where combustibles may start a fire.

The garage is a desirable location for a smoke detector. I have one installed in the garage on the ceiling above the inside entry door. It has been there for a long time and has never "false alarmed", even during the 1980's when we owned an Oldsmobile Diesel station wagon.

The secondary advantage of a smoke detector in an attached garage might be a warning of carbon monoxide if someone forgets to shut down the engine when garaging the automobile.

The only detector in my residence that "false alarms" is the one installed at the top of the stairs near the upstairs bathroom door. Steam from a hot shower will trigger it if the bathroom window is not open.

The problem seems to be not enough smoke detectors are in use, rather than being installed where someone believes they shouldn't be installed.