Understanding the consumers and making a product likewise is one of the major factors in deciding a product's fate in the market. Some products that could have been a great success failed because they failed to understand the market and offered something which the consumers couldn't digest at that time.
Talking about gadgets, it's all about what is trending currently. Your product should sync with the market's trends, or be something like never seen before (but still should be useful). So, let's have a look at some of the biggest gadgets that were a failure, and hence, fell flat on their face.