The "Check Point" app is initially a free demonstration Android app.
As initially installed the "Check Point" app is limited to 5 On Site Visitors at a time.
Purchasing and installing this "Check Point key" app removes the 5 On Site Visitor limitation of the "Check Point" app.
"Check Point key" must remain installed for unlimited On Site Visitors.
The "Check Point" app checks for "Check Point key" whenever "Check Point" is started and every night shortly after midnight. If "Check Point key" is uninstalled, "Check Point" will revert back to the 5 On Site Visitor limitation.
For Android V10 and lower, checking "Check Point key" is totally transparent to the user.