Details on the Free edition seem ... sparse. LOL
And I do not see anything that indicates it will ensure mysql and asterisk are actually working (ie: no corrupt tables for mysql and Taking Calls for asterisk ...).
Just being sure processes are running can be handled with any one of several apps (easiest of which being Webmin). But if a mysql table corrupts or asterisk freezes ... the warnings won't go out and a client will be seriously upset. We monitor both of those to allow us to fix a server before a client can complain. Merely checking to see the processes have a PID doesn't mean they are working as designed.
We stop short of actually generating a phone call for most clients, but we have a couple who insist on having calls generated regularly to ensure everything works. (So our system calls their system, their system answers and logs the call, and then our system checks the log to be sure all went as expected ...). That covers numbers being ported unexpectedly, asterisk freezing, carrier routing failing ... and of course we check for crashed tables regularly for those on the deep watch.
All custom of course, no "app" with a two-week learning curve. LOL