I fully support an @home project, but it has to pan out to a true supercomputer status of cpu power or it will take years, even decades, to crack an encryption that is probably already replaced in newer phones.
We need some stats and specs to give an idea of how much cpu time and how many people would be needed to crack sha1 in a reasonable time.
What is the size of a single sha1 hash? How long does a typical (let's say a core duo/core 2 duo powered machine) computer take to run a single operation? From there we can move on to how many operations a second it is capable of, and work our way down to the end result of: how many users are needed to crack the code in x amount of time?
I see it this way. I have a droid 2 global on 2 year contract, with 20 months left. If it cant be done by 18 months then I do not believe the attempt to even be viable, considering how many of us have droid x's and 2's and milestones looking to upgrade.
The last time I crunched some numbers, with the help of some others in ##pbf on Freenode, it seemed like it would take ~1250 years if we had 1000 actual computers working on it. With cloud computing options (Azure, EC2, etc.), a quick burst of 1000 computers (an hour or two) isn't impossible nor that expensive but it's still a few orders of magnitude away and a sustained effort would be beyond affordable. If we had a million computers crunching the numbers, we'd still need over a solid year of it.
Unfortunately, I just don't have a botnet all. Sorry.