Any PaaS or IaaS providers come up in seconds, bill per minute?

In practice EC2 instances take a few minutes to come up all the way, and bill per hour - partial hours included.

I have a very parallel workload that needs a large amount of capacity to come up in seconds, and then go away after a few minutes - paying for partial EC2 hours when I'm using the instance for ten minutes or less just doesn't make sense.

Can anyone recommend a PaaS or IaaS provider that might better suit my needs?