Simon 5 is coming soon!
Simon version 5 is currently in beta testing. It is a massive update, introducing a much-requested feature: syncing the Simon data between multiple Macs, plus a Simon Status service, a Link Checker filter, improved Find filter, iMessage and Speak Error notifiers, a new app icon, and much more.
Important: please note that Simon 5 requires a minimum of macOS 10.12 (Sierra), and will be a paid upgrade from Simon 4 after the beta. Purchasers since September 1, 2020 automatically get a version 5 license (that also works in previous versions).
Re: Web Access to the Monitor - like WhistleBlower
Yes, that was a nice feature. In Simon, you can use the Reports feature to view the recent status of the tests in a web page, but it isn't interactive — you can't control tests from the browser.
This is something I'd like to add in a future version, though it isn't yet scheduled for a release. WhistleBlower did it by running its own web server, which has some advantages, but also disadvantages, like having to make the machine public. With Simon's reports, you can do that or upload to a remove web host.