What is the usual functionality of stalkerware? The most basic thing is to transmit the victim’s current geolocation. There are many such “stalkers”, since various special web resources are used to display coordinates, and they only contain a few lines of code.
Often, their creators use geofencing technology, whereby a notification about the victim’s movements is sent only if they go beyond (or enter) a particular area. In some cases, functions to intercept SMS and call data (spyware that’s able to log them is much less common) are added to the geolocation transmission.