Maretron sells what you need and also a N2K sensor for detecting water
in the separator.
I do not agree that you will change your filter too late when monitoring pressure. Filter manufacturers will provide data on pressure readings for changing elements. Mechanical gauges with alarms do the exact same thing and they might even be more expensive than electronic monitoring today.
The advantage of N2K sensors is that you use the same displays to monitor everything and generate alarms in these central locations. On a short handed yacht you want more electronic monitoring than on a ship with more crew.
Many yachts & ships with mechanical gauges use cameras to view those gauges remotely... now that is ridiculous imho :-)