Balloon Recon

Particularly for Napoleonic (stretching early military use a bit) and American Civil War versions, balloon units can be an aerial recon that move and embark/deploy like artillery (say, a 1-hex spotting range while transported in wagons and a 5-hex spotting range when deployed).

"Federal observation balloon Intrepid being inflated. Battle of Fair Oaks, Va., May 1862. 111-B-680." (archive.gov)

Update: K.u.k. General WWI campaign uses this idea with a zero movement (when not "towed") which I think is appropriate.