I recall the PSION PDA with fondness and I have always thought that in some ways we have gone backwards as well as forwards when it comes to smartphone innovation, particularly around form factors and keyboards.
Enter the Gemini PDA which by no means follows the modern trends of smartphones and which pays more than just a little homage to the Psion. This is hardly surprising given that CEO Dr Janko Mrsic-Flogel involved prior Psion industrial designers in the build. Over at Gemini Planet they have a post which gives a good examination of retro and relevancy.