Anyone knows of a sugar substitute or a supplement that can sweeten your coffee, tea, cereal that is safe for Diabetics? I've been using Sweet n Low for quite a long time. I feel it's unsafe?

Sucralose is the most common sugar alternative that's considered safe to use by diabetics.  That being said, as sucralose is a relatively new product, there hasn't been a great deal of research conducted into the long term health effects of its consumption. 

The American Diabetes Association, however, has approved the use of sucralose by all three types of diabetics.  You can find sucralose in most stores these days, often under the brand name of Splenda.  There are, however, a few more sugar alternatives available to diabetics.

Acesulfame K

Acesulfame K is another common sugar alternative that's used primarily in baked goods.  Around 100 tests of Acesulfame K indicate that it's safe for use by diabetics.

Stevia

One of the most used sugar alternatives in the world, Stevia is often found in the form of Truvia or SweetLeaf, and is considered safe for use by diabetics.

It's important to note, however, that there are different forms of diabetes, and advice from a doctor should be sought before making dietary changes.