Normally the IDrive mobile backup service is $5 a year for unlimited data backups. (Not to be confused with the desktop version, which is considerably more expensive.) But today you can get a lifetime of backup service for just ten bucks. StackSocial is running the promotion, which will be available for another six days. If you find Google or Dropbox's backup plans too limiting, this might be worth a look.
The IDrive backup app doesn't upload each and every file on your phone, but it does grab photos, videos, music, and less tangible items like your contacts, SMS and call logs, and at least some app data. Naturally it allows you to access those files from any other mobile device (including iOS) and on the web. The app isn't exactly the most intuitive or flexible cloud storage solution, but it'll work if all you're interested in is a cheap backup solution.
IDrive's terms allow unlimited backup of up to five Android, iOS, or Windows Phone devices, and presumably the "lifetime" deal from StackSocial means you have access to the service forever. Or until IDrive is restructured, merged, purchased, driven out of business, or just plain decides to stop giving you unlimited backup. Whichever comes first. But in any case, it's at least a few years of backup services for your phone or tablet for a rock-bottom price.