[chef] Automatically starting a new EC2 instance with Chef

[Edward Sargisson < >]

Hi all,
What tools and services are available to automatically start a new EC2
instance with Chef?

My site has just one server and yesterday it failed. Unfortunately, I
was at my day job and couldn't do anything about it. It's configured
with Chef so starting up a new server with knife then using Opscode
Platform to put the roles on was reasonably easy (it could be easier
but I have some issues to fix).

What I would like is for some service to realise that my server is
down and then call Chef to setup a new one. Amazon Auto Scaling almost
does this - the issue is that it merely starts an AMI and doesn't do
anything cleverer than that. My Chef setup assumes a brand new Ubuntu
image and goes from there. I suppose that, for future use, whatever
solution I use needs to also listen to the CloudWatch metrics to scale
up and down when required.

So:
Do I write an image which bootstraps chef automatically?
Or is there some other way to solve this problem?

Thanks,
Edward