Well, the problem with the idea is that once you've melted the ice, how are you going to keep it from re-freezing? Common ice melters are generally soluble salts which melt the ice by the slightly exothermic reaction upon their dissoluation, as well as lowering the freezing point by dissolving in the water. (Calcium chloride is a common ice-melter because it can donate three ions upon dissolution which will lower the freezing point of water more than a binary salt like sodium chloride does). Those types of ice-melters are beneficial because once they melt the ice, they keep it from re-freezing.
A method you could use is a mixture of sulfuric acid and water isolated inside a device. Upon mixing concentrated sulfuric acid and water, a GREAT deal of heat is released. If you were able to do this inside a chemically inert chamber, it would create a large amount of heat. When you're done, you'd then just have to boil the solution to remove the water from it and start all over again. Once again, however, is the problem that once you've melted the snow and ice, it is just going to refreeze again once it cools off. So really, the best way is to just throw some calcium chloride flakes or pellets onto the snow and ice and let it melt it.