Hoof supplements can be a waste if your horse doesn't need them. If after 2-3 months you can't see any difference in the hoof quality that's growing down from the hairline, then it's not really adding anything the horse wasnt' getting already.
Jello is available in plain unsweetend, and yes, it's something that might help, but like it was mentioned, it's not cost effective to buy it from the grocery store in the quantities you'd need, for a large horse. We used to feed the dried milk to our horses years ago, and it did seem to help with some. But like any supplement, if you don't actually see improvement, you are wasting time/money.
However, I do feed Horseshoer's secret, the maintenance dose to one of my horses and it DOES help him, andI certainly don't think jello would do the job. The Horsehoer's Secret doens't have the highest level of Biotin, but it has a mix of other key nutrients that maximize absorbtion. Straight biotin isn't effeciently used by the horse. THe methoinine , lysine, etc help the horse utilize it. For the money H.S. Secret is the most affordable EFFECTIVE hoof supplement I've found, but I only feed it to one of my horses, the other doesn't need it.