I agree with what the others are saying - get a "real" alarm system. If you want to DIY to save money then the Ring or SimpliSafe. Keep in mind these systems will have been thoroughly tested for that purpose so are likely more accurate/less error prone.
Ring has a nice set of integrated devices that you can build off of so would probably start there. Doorbell, Floodlight Cams, and alarm system. In terms of linking with the Hubitat you could use a HomeBridge server and/or Node-RED. Otherwise as others mentioned you can use Ring devices directly with HE which is nice. NOTE: device is either paired with HE or the Ring system NOT both. Also there is this possibility as well:
Looks like there is a community driver for SimpliSafe.. have not used this though.
