If everything you have to lose is time (that might be the case if you are a good website developer&designer for example, and also can make the product yourself), then you should give it a try - why not? Same idea does not mean same product. You could become more successful than your competitor by having the better product.
If you need to invest a lot of money at first, it's different of course. Then nobody can help you with your decision, you should analyze the situation and decide on your feeling.
My thoughts: If you don't have a good feeling already (and I don't mean if you have a bad feeling), then you should just leave it. You should be amazed by your idea for it to work.