Is there a way to build a droid that is almost as good as the heal force power? I have seen a character with force heal, heal critical wounds and most of a player's wounds and strain to full health.

Technically the Droid character can purchase all 3 Healer type Specializations, starting off as a Colonist Doctor or a Soldier Medic, then picking up the other and the Consular Healer tree. The Droid would be able to purchase the talents in Healer, they just wouldn't be able to use any of the Force talents but there's some pretty great stuff in there like extra ranks of talents from the other 2 trees that could further increase healing as well as the Knowledgeable Healing talent which doesn't show up in the other 2 healer trees and allows you to spend a Destiny Point to heal additional wounds up to your ranks in Knowledge (Xenology). High Intellect, Medicine skill, Knowledge (Xenology) skill, & good equipment will help. A medpac gives you a boost die on all medicine checks & provides a stimpak per encounter. An Intellect enhancing brain implant will increase your Intellect characteristic past 6 and into 7. Starting as a Colonist will give you the option to pick up the Colonist Signature Ability that allows you to reduce the difficulty of any 1 check you make per session.

Now all of that won't really aid you in repairing droids or ships other than anything that increases your Intellect since Mechanics also goes off your Intellect.

Great suggestions from GroggyGolem, but be aware that that sort of monotask specialization basically makes you a well-used 2-1B surgical droid. Like any other specialist, you'll encounter a lot of situations where you're out of your depth, though those three Specializations will give you an... interesting list of class skills. Droids excel in the specialist role but they can be a challenge to roleplay, for both you and the rest of your group.

For in-combat healing, look to maximize Stimpack Specialization. We had a Soldier (Instructor/Medic) that could do amazing things with a handful of stimpacks.

Nothing is going to heal Strain or Crits like the Heal Force Power, but as HappyDaze said a Medic/Instructor or Medic/Protector can have 5 ranks of Stimpack Specialisation, so thats 10 Wound son the first jab, 9 on the second. not many PC's have more than 19 wounds. even the last 2 of your 5 for the day will net you 13 which is seriously good. If you have plenty of xp to burn then there are 7 ranks total available, a mighty effort if you ask me.

Inspiring Rhetoric can help your allies heal Strain, and even though the supreme version can be done as a manoeuvre its still only healing 2 or 3 Strain to a target and 1 to everyone else.

So as I started out with, nothing is going to compare to the speed at which Heal can repair Critical Injuries, Strain and Wounds all at the same time, in the middle of combat... its just going to take a heap of XP to do it reliably.

Your GM may even allow you to select Stimpack Specialization as a battle scar advance. If your scar is psychological from seeing your buddies gunned down while you're trying to heal them, it makes some sense.

Are talking healing in general? If so you can get pretty close. There are aspects of the Healing power though that aren't replicated with spec talents.