Improving crit-range of touch attacks possible?

[Diminutive Titan]

I have a question;

Is it possible to increase the threat range of melee touch attacks?
Or maybe the better wording of my question would be:
What is the maximum crit-range you can get with touch attacks?

I am not talking about a Magus who could deliver it through a weapon, I'm talking about any other spellcaster.

Is it possible to take the Improved Critical (touch) feat, if sufficient BAB?

Or is it better to deliver touch spells through natural attacks? Although I believe it shouldn't change much because all natural attacks have a 20(×2) multiplier?

Your thoughts?

Thanks in advance,

DT

[Nefreet]

Give your Familiar the Critical Conduit feat. It's worked wonders for my Magus's Quasit.

[KahnyaGnorc]

If you have a Natural Attack (or Unarmed Strike) that deals Slashing/Piercing damage, you can benefit from an Amulet of Mighty Fist (Keen) or a +1 Keen Bodywrap of Mighty Strikes.

[Imbicatus]

KahnyaGnorc wrote:

If you have a Natural Attack (or Unarmed Strike) that deals Slashing/Piercing damage, you can benefit from an Amulet of Mighty Fist (Keen) or a +1 Keen Bodywrap of Mighty Strikes.

This works, but note, you are no longer targeting touch AC if you do this, you are targeting full AC. On the plus side, you get your unarmed/natural attack damage as well.

[AerynTahlro]

Improved Critical would work just fine.