Under the RAW for "Throw Splash Weapon":
A splash weapon is a ranged weapon that breaks on impact, splashing or scattering its contents over its target and nearby creatures or objects. To attack with a splash weapon, make a ranged touch attack against the target.
The RAW makes no distiction between a ranged touch or a melee touch:
[T]he attacker makes a touch attack roll (either ranged or melee).
Hitting an ally with a ranged touch attack allows them the opportunity to declare themselves to be a willing target:
Declaring yourself as a willing target is something that can be done at any time (even if you're flat-footed or it isn't your turn). Unconscious creatures are automatically considered willing...
Seeing as willing is the equivalent to the "Helpless" condition:
A helpless character is paralyzed, held, bound, sleeping, unconscious, or otherwise at an opponent's mercy. A helpless target counts as having a Dexterity of ZERO (-5 penalty [to their AC])
So, then, an Alchemist can throw healing bombs at their allies with minimal effort, only needing to account for size and (possibly) Luck.
As an aside, a thrown splash weapon can even target empty grid spaces at DC 5.