Question: My niece is 15 months old, and has inherited a combination of the worst traits of her parent's hair: it's very very fine, like her mother's (and mine), and grows at all sorts of odd angles, like her father's. It's now gotten long enough to hang into her eyes, but it's not long enough to be tucked behind her ears. We fight a never ending (and losing) battle to brush it out of her face.

* Cutting it seems like a temporary solution at best, because it'll just grow again. Plus, I can't imagine getting her to stay still long enough to even attempt a haircut.
* Barrettes and clips slide right out. If gravity doesn't do the job on its own, the niece does her head shaking thing and out flies the clip. (Which she then promptly puts into her mouth, but I digress.)

	+ Yes, we've tried the various "non-slip" barrettes with rubberized this or sticky that or whatever. They're obviously designed for way more hair than my niece possesses.
* Rubber bands stay put only slightly better than clips. And as soon as she notices that there's something in her hair, she grabs it and takes it out. (And yes, puts it into her mouth.)
* Headbands (either the plastic arc type or the large rubber band type) are a lovely toy, but are not to go anywhere near the head. At least according to my niece.

I find myself wondering if they make hair gel for toddlers. Help?

Answer: 
Why is at a concern? Do you really need to worry about it?

I don't see that there is a safety or hygiene issue with hair hanging in front of the eyes. About the only thing I can think of appearance, which is fine, but not all that urgent.

It sounds like you have exhausted all of the alternatives except the hair cut. If it really is necessary to control the hair, then you need to get it cut.
Why don't you take her with you and get her to select a nice colorful cloth elastic head band? In my experience it keeps the hair out of the eyes and gradually conditions it to grow or set in the other direction.