HomeKit Ecobee Humidifier Control Question

Going to be adding an AprilAire 600M to our house and have a dumb thermostat currently. Want a thermostat that can control it and connect to home assistant locally. Seems like that leaves me with Ecobee or Venstar. With the HomeKit integration, do you have full humidifier control from HA via Ecobee? Anyone do that and then add additional sensors and their own algorithm to set humidity target (e.g., extra sensor in return duct tied to HA too to have like AprilAire 60 kind of automatic control with even more capability/flexibility with HA)?

I have an Aprilaire 700M (a powered variant, rather than a by-pass humidifer.)

My ecobee3 controls it, via the ecobee App, HomeKit or Home Assistant.

The following attributes are available in Home Assistant:

min_humidity: 0
max_humidity: 100
available_modes: off, auto, manual
action: humidifying
current_humidity: 50
humidity: 44
mode: auto
device_class: humidifier
friendly_name: ecobee3
supported_features: 1

One caveat, when you use the Frost Control mode, and set your window efficiency so that you do not get condensation on your windows, the ecobee uses the outside temperture to automatically dial-back the humidity, but the only thing that shows to Home Assistant is the set-point before the Frost Control intervention.

I’m fairly certain you could come up with your own formula for setpoint x outside temperature factor. There are look-up tables online too.