The various ways friendly retail can be supported should all be laid out here, with detailed analysis of how different technologies might apply. That means there will be some redundancy with the technology explanations, like DECT, but that's impossible to avoid: this friendly retail page must be complete and convincing on its own, so it can be printed and handed to any potential partner. You can't ask such people to read everything on DECT or GSM, you have to selectively quote convincing information in this article.
Also the whole healthy signal infrastructure has no choice but to incorporate DECT for e-waste reasons and for simple sanity. The existing horror of POTS plus WiFi plus GSM/cell isn't going to last very long, it's a mess, and it's waiting for a unified standard like DECT to kill it.
Can't happen soon enough!