Hi Ivan
Unfortunately this is a long running issue / deficiency which has not been solved / enabled with the current releases...
We, in the UK, would like to use OS British National Grid but have to collect data in WGS84 and then transform using the geoprocessing tools...
It might be solved in ArcGIS Mobile 10.2.1 or 10.3 but I'm not holding my breathe...
We are now looking at Collector / developing our own Runtime Apps instead as I'm not sure there is much more development planned for ArcGIS Mobile.
Hope this helps
Cheers
Tim