I have designed and started work on something along these lines however the market watch part is not the primary focus. The main idea is to be informed and optionally notified when a token I care about changes (i.e., description changes, new issuance, etc.) Also there would be support for interactions between the holders of a given token. There would also be options for token issurers to provide a lot more information about their tokens and to optional take advantage of additional services to market their token and/or support their token holding communities.
Importantly the platform will target multiple 2.0 platforms running on various blockchains. I see huge problems ahead as these 2.0 platforms come online. For example if a popular token is available on counterparty, you can bet someone will create a token with that name on nxt or dogeparty or such and try to scam people. My platform would try and deal with that by clearly highlighting the copy cat tokens.
I am building the core platform with Dlango/Python but if a Javascript developer wanted to help me with the front end, I would certainly listen. Eventually mobile apps to access the platform would make sense too.
