While Linux mobile shells are still in a very early stage, touch-optimized app launchers can significantly improve the overall user experience on touchscreen devices while using less memory than a full shell. Some of these close automatically each time an app is launched, so associating them with a particular hardware key on the mobile device might work.
There are several simple Linux launchers available, columbiad is the only one officially packaged:
- lxlauncher (LXDE official launcher, gtk2; screenshot)
- columbiad (minimal gtk3 fullscreen launcher; video demo; merged into aports)