Follow along with the video below to see how to install our site as a web app on your home screen.
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Your going to have to root your backflip before you can install outside of market.
Yep, I installed PDAnet on my Wife's backflip last night using ADB. No root required.
PDANet and EasyTether will show up in the market if you remove the SIM from an AT&T Backflip and connect via WiFi. Some other apps that usually don't show up also.
One site that you can get apk files from is www.slideme.org it is a different market from Google and has plenty of apps that you can download to your desktop. If you have an installed app that you want the apk from; install Estrong, then use Estrong's backup feature to backup the app (a button that looks like a set of gears). The app will be copied to your storage card's download folder. Then just copy the apk file to your computer