Mozilla are working on a very similar implementation at the moment in Boot2Gecko. I personally hope to see this be brought inline with Intents with feedback ab

Mozilla are working on a very similar implementation at the moment in Boot2Gecko. I personally hope to see this be brought inline with Intents with feedback about what they have learnt in the process. Web Intents does have a compatibility JS shim, it needs a couple of updates to get it working in FF again after implementing Content Security policy, but after that WI should work fine (but not native).