I doubt that thing will melt the ice under the snow anyways. It would probably take really long time to melt the ice with that and when you do that you effectively start blowing away the road too. Probably what is left after that thing has gone is slush. That of course freezes into ice and snow again but it is not slippery flat ice but something that is still kinda slippery but not dangerously so.
Haha yeah that's a clever but lazy way of "fixing" your speedo.
I do a similar thing but the exact opposite, the cheapo rpm gauge on my daily is a little too slow to react so I actually have learned to use the speedometer in first and second gear to indicate my shifting points. IE. I know that in second the rpm limiter will cut off at just below 110 km/h so I will shift up when I see the needle going past 100.
Hint. don't buy Autogauge rpm gauges if you want a tacho that will react to a quickly revving engine.
Cheapo rpm gauges used to be much better when they were analog gauges.
-EDIT Same goes to those cheap chinese monster tacho knock-offs. A worn out Lada engine could out-rev them.