My adult son has been using Proloque2go for years, with a 4th generation iPod in an iMainGo 2 speaker case. I started looking for a replacement for the iMainGo when the 5th generation iPod came out, and I realized that the company that made the iMainGo went out of business (and a new model that would work with the larger dimensions of the newer iPods wouldn't be developed).
What is everyone else using? My son carries his device with him all the time, and it suffers some major hits -- so it needs a case that is at least as protective as the iMainGo. And, he needs the ready-access that the plastic screen on the iMainGo provides. (All the other portable speaker units I've seen have the iPod enclosed in the case, so you can't use it without stopping to open it up.)
It's getting harder and harder to find "new old stock" iMainGo units -- and I'm getting tired of the work around you have to go through to load the 3.0.3 version of Proloque2go on the older iPods (and the older iPods are getting harder to find too).