Am pretty certain, if we could produce a hedgerow cam in the seventies, would can produce something much better today and a casual search reveals many suppliers and types of system, from the ubiquitous ‘nanny cam’ and ‘rock cam’ to ruggedised low profile Inmarsat BGAN terminals linked to advanced thermal imaging cameras.
There are all available now, and nothing unique.
Seraphim in Israel are a typical supplier of high end persistent ground surveillance equipment.
It is interesting that Seraphim market some of their systems as ‘unattended gap fillers’ because that is exactly what they do, personnel and other systems cannot be everywhere all the time.
Long endurance power cells are also available, the example below is from SFC Defense
Cobham also have a range of systems for covert surveillance.
But despite their availability these kinds of systems have not found widespread use in all but the most specialised and limited scenarios.
The simple reason is one of bandwidth availability and high cost, plus the ever vexing question of how to turn huge volumes of data into useful intelligence in a timely manner.