Hi David, Could you clarify what you mean by 'remotely connected'? As in, sending detections over wireless transmission? Allowing adjustment of configurations? That would help the community narrow down possible recommendations :) 

So we are building some Bugg devices on licence from Imperial College, and I am making a mod to change the mic out for a version of out Demeter microphone. This should mean we can use it with something like BattyBirdNet, as its powered by a CM4. Happy to have a chat if you are interested. Else it will likely need a custom solution, which can be quite expensive!

There are a lot of parameters in principle here. The size of the battery. How much time in the field is acceptable before a visit? Once a week? Once a month? How many devices you need? How small does the device and battery have to be etc. I use vpns over 4G USB sticks.

I ask because in principle I've build devices that can retrieve files remotely and record ultrasonic. Though the microphones I tested with (Peterssen) are around 300 euros in price. But I've been able to record USB frequencies and also I believe it will be possible to do tdoa sound localization with the output files if they can be heard on 4x recorders.

But we make commercial devices and such a thing would be a custom build. But it would be nice to know what the demand for such a device is to know at which point it becomes interesting.