The idea is great !! Its not new though..
Check out http://www.pounce.mobi/ ( it was earlier called BuyCode).

Some positive points
1) Just because it is there, it does not mean you can build it.
2) A business which got acquired and vc backed is a good sign that your idea is already market validated.
3) Because it is validated, you already know what is the market segment you need to target or you can pivot from the known reference point now.. cool ..isn't...

How can you do it ?
1) Ideas are dime a dozen and worth a shit. Don't feel bad. Build an MVP.
2) With the image recognition already democratized using dozens of cloud service providers, you should be able to build something quick with low TCO (total cost of ownership).
3) Identify your business model. You want to copy BuyCode or do something different ?
4) Try selling it - (rubber meets the road). You will feel the heat and smell the burns :-)

Need help ? talk to me.