Are you concerned about small children eating leaves or berries? It is usually simplest just to train them not to put plant parts in their mouths, or if too young, keep them under supervision. Unfortunately, the vast majority of common landscape plants (and a good number of edibles as well) ARE going to be toxic to some degree or another, but toxicity will vary widely with plant and amount ingested. It is a bit easier to start with plants that will work for any given growing situation and then go through and elminate those that might pose potential danger. For standard hedging plants, that eliminates boxwood, hollies, privet, yews, laurels, mock orange, juniper, oleander and podocarpus and a number of others.

You don't indicate how high a hedge plant you need, but you might consider lavender, rosemary, germander or other woody herb (all edible) or something pretty unappetizing (unless a deer or cow), like ornamental grasses. Or click on the other link ("Safe Plants") at the bottom of the UCDavis toxic plant website for additional possibilities.

Here is a link that might be useful: UCDavis toxic plant listing

Again you haven't indicated how tall or dense this needs to be, but if it doesn't need to be too tall I once planted espallierd (sp?) apples and they were lovely .( A rail fence effect, they were purcased pre-trained at a local garden center). A neighbour took up the idea and ran with it and put in pole apple trees, planted 2ft apart alternating at 45 degree angles (1/2 sloping up to the right and half to the left) This gave her fence the effect of about a six foot tall latice. They were both very pretty, with a lot of visual impact in all seasons. They tend to be expensive and do require some summer maintenance pruning, but you might not need all that many. And they are realy, truly, non toxic.(yum).