AirStats has no accounts, no ads and no tracking. What it reads from your Mac stays on your Mac.
The app
AirStats reads processor load, memory, temperature, storage and network activity on your Mac. It does not send those readings anywhere.
AirStats connects to the internet only to check for updates and, if you turn it on, look up your public IP address. You can turn automatic update checks off in settings. The public IP display is off by default and clears the address when turned off.
Nothing else leaves your Mac.
This website
The site records anonymous, aggregate statistics such as page views and load times. It has no accounts, cookies or ads, and we do not sell visitor data.
Questions
Email for anything about your data, or ask on the issue tracker. The app is open source, so you can also inspect how it works.