FINALLY, someone who had the same idea as me. I've actively looked for ways to do something like this and even considered setting something like this up in a quick and dirty way (by abusing X forwarding over the internet across devices; probably the closest I'll get to making this system work without modifying every program on my computer).
The sheer inefficiency of getting my email on my phone, laptop, PC and tablet across several apps without any of them communicating between them is driving me mad.
I have an overpowered gaming machine in my room and a slow, old Samsung tablet near my bed. If I want to read something in bed, I'll have to suffer through the slow Chrome browser with all of its lag and lack of hardware accelerated decoding while there's a machine with incredible graphical power available _right there_. I'd love to turn my tablet into a thin client for my PC, but that requires a mix of slow or unstable remote desktop apps.
In my mind, this concept would also have other devices help with the workload. For example, when my server is busy running compilers, my laptop can kick in and help out with some of the work by doing the Javascript for my tablet. This makes the work more complicated, but combines the power of my collection of personal devices into a single platform.
I really hope someone or some company can help the world move this way. It's been done before in part back when thin clients were the latest hit and after the last few years, responsive design has been normalized to the point combined systems like these have a real chance of becoming the next thing in computing.
Sadly, I fear the moment this becomes popular the general population will just pick a cloud-based solution so they don't need to set up an application server, which gives companies like Amazon and Google even more power and data then they already have.