I've pondered/meditated on this topic A LOT over the years. The current problem in regard to our spirit friends is identifying an energetic signature for that specific person. To date, there is just too little known about the subtle energies involved in their "form."
For a living person, this type of automation could be done with sensors for biofeedback. For example, once a medium reaches a theta brain state, a trigger could be developed that takes an action...say, begins recording audio.
But the real problem is that our technology seems to make little difference; we're never the ones leading the way. We're just along for the ride. This dream would most likely need to be achieved by spirit teams working to bridge the gap back to US.