If the niche is electronics, as you said in the question in your other post then it's really not a niche it's a broad and VERY competitive product category.
Electronics is pretty competitive no matter how you cut it, so even if you drill down to a sub category it may still be tough.
Possibly if you know alot about and have a special interest in one very specific type of electronics you could do OK if you are good at marketing. Does not have to be a single product - could be several production options in the same niche category like GPS or radar detectors. But something like digital cameras would be extremely tough as far as competition goes.
You need to check # of searches compared to number of competing pages.
Most keyword tools call it KEI. Here is some info:
KEI - Keyword Effectiveness Index - Identify keyword that are easier to achieve top 10 rankings
More info here:
Keyword Effectiveness Index (KEI)