I have searched extensively for a rain gauge (and temperature perhaps) that can be connected to POE or a home wifi connection.  

All the remote weather stations that I can find for sale connect to an inside screen using a battery powered propriety wireless connection. Some of them then upload to a service for viewing but in most cases it is fairly basic, particularly the inside viewing panel.

In this day and age it is easy to purchase a camera that constantly streams its data that can be accessed from any internet connection and viewed on any device such as a mobile phone app without an intermediate device in the house - why is there not a weather station or a rain gauge like this?  Other consumer devices such as window and door monitors or even smart switches and bulbs can be remotely read or actuated using apps and don't utilise their own independent wireless connection and panel.

POE would overcome one of the weak points of the current selection - flat batteries.  The system could be attached to the ridge or gutter of the house and a network cable attached from the router via the ceiling etc.  I also envisage a marketer optionally monetising it by recording the data over time and presenting it for a small annual fee.

There may be a number of professional and expensive units available that I have dismissed because I only require a domestic grade system, perhaps similar in cost to a reasonable consumer grade camera.

I have mentioned the above in this forum because there may be someone out there that would welcome a challenge and may see an opportunity.  In my mid 70s I have too many rings in my trunk to give this a nudge.