Saturday, Amazon released a new app with functionality similar to Apple's Photo Stream. The app, called Amazon Cloud Drive Photos (free), automatically backs up your iPhone photos to Amazon's Cloud Drive. You can access your photos via the web as well as share them via Facebook, Twitter, and email. The beauty of this, of course, is that your photos are secure in the cloud even as you take them. Without even having to manually upload them, you can access them via any web browser. Amazon gives you 5GB of free storage in its Cloud Drive, and lets you store up to 2,000 photos. Apple's Photo Stream, which is built into the iPhone, is similar, except that it limits you to 1,000 photos. Another serious limitation is that your photos in Photo Stream expire after 30 days. With Amazon's service, there is no time limit. You can store your photos for as long as you want.
If 5GB isn't enough space for you, you can pay for additional storage, (e.g., 20 GB for $10 per year, 100 GB for $50, and 1 terabyte for $500.
The app isn't quite as automatic as Photo Stream, since it must be running in the background in order for the photos to be uploaded automatically. And you first must enable automatic uploading and authorize it to access your Camera Roll. Plus, of course, you'll need to set up a free Amazon account if you don't already have one.
If you're on a limited or expensive data plan, you can set it so that it only uploads the photos if you're in range of a Wi-Fi hotspot.
There's really no reason not to use both services. You can be doubly secure. One interesting and additional difference between them is that Apple's Photo Stream will only let you upload photos via WiFi, whereas Amazon's app gives you the option of using your data connection.
The app is optimized for the iPhone 5, and compatible with other iPhone and iPad models, but there's not yet an iPad-specific version.
Of course, the functionality of Amazon's Cloud Drive Photos extends beyond the iPhone. You can also upload photos via your desktop computer and then view those photos via any device connected to the Internet, including your iDevices.