Hello Personally I don't use my DSD buttonbox anymore, I have since a virtual buttonbox VDASH-EMU with a controller Virtual To Real (V2R) that works exactly like my old DSD for $25 ($5 for the VDASH-EMU + $20 for the usb controlleur) with my Android tablet but with much more possibility. I can create a page for each game with the buttons I want, it's super flexible and powerful. see here: http://www.eksimracing.com/eksimracing-firmware/
Same for me : everything is possible To use it is not to be able to do without it! creation time of this page 5 minutes !! (android tablet)
But it not the same. You can't turn that knob. Besides, I recently prepared an order for parts needed for diy box and it ended up around 50 euro so more or less the price of a cheap tablet alone
today almost everyone has a tablet? or a protable! no? Edit : You can't turn that knob Yes, Up/Down with your finger on knob (Encoder)
obviously not the same as a PHYSICAL button but yes you can turn the knob using gesture... with VDASH-EMU + a V2R USB Controller you can setup more than 40 pages for your custom virtual buttonbox for each game or simulation and you have up to 128 buttons available... it's a good alternative to a physical buttonbox, IMHO.
It's still not the same. You can locate physical objects like buttons and switches without much looking. You can't do that with virtual button box. And swiping is not the same as turning. I wish you luck with your product though.