It's worth having a VPS around as your dev environment. The laptop you're carrying around is extremely likely to get lost, stolen, dropped, or otherwise damaged. A VPS isn't a backup solution, but it's not at constant risk of physical harm.
Work in a screen session and you'll be able to pick up where you last left off --from any machine. Not to mention your VPS is almost certainly faster than your laptop and connected to a bigger pipe than whatever wifi you're borrowing, so downloading a .tar.gz or a git clone will be fast, and compiling won't eat up your battery life.
It's probably worth plugging http://prgmr.com/xen/, run by fellow HN member lsc. If you prepay for the year, a 256MB VPS is only $6.40/mo. I've had good luck with it so far; it's a perfect always-on dev environment.
(I'm just a customer, no affiliation)
Edit: looks like they're not accepting new customers right now. sorry.
They where having some issues with their billing pages it said for some time. You can always email them and ask to keep you updated when you can place an order again. Even tough they seem to cut costs by not having a regular helpdesk, they are very fast responders and seem to know their bussiness very well.
I'm a new customer of their service and very happy with the price/quality, but you do have to have a technical background.
Work in a screen session and you'll be able to pick up where you last left off --from any machine. Not to mention your VPS is almost certainly faster than your laptop and connected to a bigger pipe than whatever wifi you're borrowing, so downloading a .tar.gz or a git clone will be fast, and compiling won't eat up your battery life.