That product has been requested from when the UnitQute debuted (if not before), but Naim seems to be in no hurry to produce one. Eventually they'll probably have to.
I'm toying with the idea of a Sonos connect plus (eventually) a decent DAC. An entry level streamer from Naim (and an android app) would be very tempting, it would also provide a steady upgrade path
An entry level streamer would be great for someone with a Nait 5i. The other option is to get a DAC and Squeezebox (or Sonos as you suggested). The trick would be to find a DAC that has synergy with the Nait.
For all practical purposes the UnitiQute is Naim's entry-level streamer. After that you're looking at the ND5 XS, and don't ever expect them to release a dedicated streamer below that cos they have 2 further up, plus there's the original Uniti, and the new SuperUniti.