Konnected is great for bringing all the sensors into Hubitat and you can add a wired siren as well. They also make an integration board which let you keep the existing alarm system and just makes the devices available to HE if you'd like to keep that alarm system.
HE doesn't really have a alarm monitoring solution right now however you could look at Noonlight as you can make a virtual switch and make that available to them and turn it on when your HSM is activated and it will alert them (I haven't tried their service).
Blue Iris is a great NVR product if you are interested in loading it on a Windows 10 "Server" with a large HDD. It integrates locally using BI Control with Hubitat to let HE change its profiles (notification, and recording rules) based on HE Modes so you can have internal cameras only record when your away and outside cameras motion settings different during the day or night to help eliminate false positives from sun/shadows. However it requires IP cameras or at least coax to IP converters added to the cameras.
