In reply to captain paranoia:
Update:
Having tried* quite a few 'UPnP apps' from Google Play, the most promising one so far is UPnPlay:
https://play.google.com/store/apps/details?id=cx.hoohol.silanoid&hl=en
This is a a 'media player', in that it includes the UI and DMC functions to allow you to browse a DMS database, but it also makes its renderer visible to the network, which many other players don't (it's not enabled by default, though; you have to change the obvious setting).
When started, it can be put into the background (i.e. you can return to Android's home screen and use other apps), and it will still play. I left the broken screen tablet plugged in last night, with the screen off, and used Kinsky to send music to it this morning (after being idle overnight), and it started playing straight away. It can have its volume controlled by Kinsky.
The only down side so far is that the track playing doesn't seem to appear in Kinsky's 'Now Playing' area, although it does show in the playlist. I need to check the settings to see if that can be sorted.
It plays MP3 and FLAC, and it's fairly lightweight at 2.5MB.
* Other things I tried:
Bubble UPnP: DMC/DMR renderer public, runs in background, pay for app
MediaMonkey: DMC/DMR renderer not 'public'
UPnP Monkey : DMC/DMR renderer not 'public'
VPlayer: DMC/DMR renderer not 'public'
Droid UPnP: DMC/DMR renderer not 'public'
Gingko DLNA: DMC/DMR renderer not 'public'
When I say 'renderer not public', I mean that I couldn't find an obvious way to make its renderer visible to other UPnP devices (e.g. Kinsky DMC). It may be possible, but not via a control setting that I could find.
Some of these may also offer DMS, either built-in, or as an add-on app.
MediaHouse: DMS/DMC/DMR: renderer not 'public'
XBMC: DMS/DMC/DMR: renderer not 'public', aimed at big screen UI, rather heavyweight. Would be great for making a Smart TV system I suspect.
Smart DLNA: couldn't make this supposedly DLNA compliant player do anything useful...
AirPin (formerly AirPlayer): DMR, but has to be foreground, and goes to sleep after a while (so it wouldn't have played this morning like UPnPlay did)
To try out:
AirWire
Mirage UPnP