[pseudohadamard]

For in-house monitoring it's tricky because pretty much every vendor who makes more than bare-bones ones goes out of business or discontinues the product 12-18 months after you've bought it (Air Mentor, Awair, BlueAir, EdiGreen, Foobot, the list goes on). The best one I've found are QingPing, colour LCD touch-screen display with WiFi access, been around for years, regularly update the firmware and hardware, actually provide real product support, and have things like MQTT integration if you're using HA.