Simply put, you as a recon can see the enemy's hp %. This would aid them in knowing when to fight and would be fun to see how much your attacks really do (would probably help the Data gatherers too).
Much like how the Solemn Vow allows the TF2 Medic to see enemy health and other info, this would help recons aid their team.
Note: you can't shield/cloak and type at the same time (without some unusual configuration) so this would be helpful (to the team) only once the recon dies and the one who killed him doesn't run and heal (if the recon tells anyone).
I think it'd be great to have team passives. Recon could see enemy health (think: enemy health bars above their heads), guardians could see friendly and enemy shield gauges (so they know when to strike), and maybe strikers could see charge bars?
All should fit into the styles of play:
Also, you could have just mentioned the TF2 Spy can see enemy health, because a recon has more in common with that class than the medic.