Custom Health Monitor

I'd like to write an http health monitor that has some conditional code in it, but it doesn't look like I can do that with the normal health monitoring configuration interface on our Big-IP system.

Specifically I'd like to hit an endpoint on each node in the pool, pull down a JSON file that describes other endpoints to check, and then roll through the described endpoints. I know I can just make a monitor for each endpoint described in the JSON document, but then if the endpoints change due to a code update the nodes will be taken offline. That same code update will also change the contents of the JSON file, so automatically reading that file and using it would be best. Is there a way to compile truly custom Health Monitors or use an iRule as a health monitor?

Thanks!