Their cheaper tags are not for freezers, at least for commercial low temp applications. But the more expensive ones work in freezers
I have really only used these for refrigeration and monitoring access to liquor cabinets in a commercial environment. I user their apps and have some notifications via Pushover.
I have a back burner project to integrate their open/close switches with our Hue Lighting. But have only researched the possibilities. But their website describes how to setup lots of automations and integrations