Ok, came up with a possible solution. Creating new building type facilities with an "eyeball" sensor feature would involve making new entries for every non-mobile unit in the database. Not going to do that.
However,based on your request there is a new "sensor" in the database called "Generic Eyeball with Binoculars". This sensor is air, surface and land capable has a 360 degree field of observation and a range of 25 miles. Considering surface coverage I think 25 is more reasonable than the 50 miles for the Mk.1 eyeball.
The sensor allows for IFF (identification friend or foe), class classification and continuous visual tracking.
To add it to a facility like a building select the "sensor" option on the "Unit Status" panel. Add the bottom of the popup screen is the option to "Add Sensor" where you can add the new "Generic Eyeball with Binoculars".
Unfortunately this new feature will not appear in the next DB3K release but will appear in the following update.
Hope you can use this.
Stilesw: That is probably a better choice. IMHO, just because every facility has people with eyeballs, doesn't mean that they have the training, motivation and communications facilities to timely and accurately report what they are seeing to the appropriate command element. By making this an optional sensor, you can create such facilities as a WWII era Observation Corps site, while not having every church, power plant, and tunnel giving timely reports of a B-52 heading to the NW at 50,000 feet