Two goals here, to power it on solar and by adding low power RAM to SPI like the https://github.com/TUDSSL/ENGAGE -they used 512KB FRAM by Fujitsu by QSPI on an Apollo3.
The solar part would be an upgrade from the AM1417 panels they used, either AM1816 or PowerFilm LL200-2.4-75 panels, which can do 1.9mW at 1000 lux. That would be more than the active consumption of the Artemis (576uW at 6uA x 96mhz) I bought a DFRobot Solar Power Manager Micro and would use a small 40mah-100mAh battery- the smallest I have is 650mAh currently.
As for application, well, I am not interested in emulating a ROM like Tetris, but am curious of running a Word Processor/Typewriter or FreeRTOS with window, icon, menu, pointers maybe on FreeRTOS. Some very basic, that could run continuously under a desk lamp, without needing to plug in.