Xylitol is a sugar alcohol naturally found in fruits and vegetables. It's as sweet as sugar and commonly used in sugar-free gums, toothpastes, and mouthwashes because it helps prevent cavities. I've never heard of it but I recently discovered that I've been using a toothpaste with this ingredient for years. Last year, I also used a mouthwash with xylitol in the ingredients list. Maybe I'll get it again when it's on sale. In both products, xylitol is way down the list and sorbitol, another sugar alcohol, is listed closer to the top.
I haven't come across a xylitol sweetener like Splenda and Truvia though. There is a product called XyloSweet by Xlear and it's available locally in my area. The two locations are specialty health stores so that's why I haven't seen the product before.