Making HP Bars visible to a limited amount of Player

Hey Guys,  I use Roll20 for a long time now but this special kind of problem never occured to me. Dungeoncrawling is a big thing in our games. Including multiple rooms and enemies with different powerlevel etc. As Gm i try to hide as much plain non-rpg information from the Players as possible (for example: Hp of enemies, stamina of enemies or chances of succesfull spells). Despite that there are options inside the Game which unravel these informations, a mage can cast spells like 'detect essence' to see the physical status of the enemy. Which results in: knowing the percentage HP of the NPC's as a player. In the last months of playing i always markes the HP bar of Monsters as visible when someone casted the spell. Now i want to add a little bit more tactical depth and only give the caster of the spell the information so he needs to communicate as a player and let the others know. Long story short / tl:dr Is there any way to let only 1 player see the HP bar of a token ? (without giving only him control over the token, cause that would result in him seeing the number of HP, where i only want him to see the percentage) Im thankful for every answer, please excuse my bad english grammar, since im not a native speaker. Hope we find a solution,  best regards, Paro

There isn't a way to do that, but you could setup a macro pretty easily that would whisper the percentage to him: /w ?{who} Creature is at [[ [[floor(@{selected|bar1}/@{selected|bar1|max}*100)]] ]]% of max health. You could modify that to use target to select the token to whisper to, or the target to inspect, or both.  Putting the calculation in double [[ ]] means only the value shows up, not the calculation, so no peeking at the numbers.

What about sharing the token proprietary right with said player?

@Aaron thanks alot, this seems like a very nice option. @Seiku because if the player has proprietary he can see the exact number 72/120 instead of the percentage as HP-Bar.