It depends of what you mean by 'Emotional Intelligence'.) If it is the hype which began with the book - well, it is overrated, and just hype. But if you think of the thousand years old Asian tradition of cultivating and maintaining a "balanced self" (via Indian meditation techniques or Asian Zen practices - doesn't really matter) then try to find anything more underrated. Losing the balance, losing ones face is considered to be very disgraceful and shameful event.)

The more clear way could be this: consider that so-called "emotional centers" in a brain (close to the center) are much more "ancient" than those in the cortex, which is a relatively "recent development" (we, presumably, share "emotional centers" with higher mammals). Thus it is very important (I would say - the most important) "part" of our brain - the world is non-verbal, it is "physical".

So, "training to develop of gaining and habitual maintaining of a fine control over these centers via breath techniques and other practices" which is called "meditation" is a very important aspect of one's personal development, especially in so-called primitive "cultures of honor". The results we could see in these "tranquil" south Asian and Indian cultures.

And, of course, the book and resulting hype is nothing but re-telling the same ancient ideas for a modern stress-ridden, anxiety-prone, ignorant busybody consumers.

A much better book, by the way, is the "7 Habits" classic. Same ideas, different context.