We have been using the Geneq iSX Blue II for around a month now, paired via Bluetooth to iPads running the Collector app. The GPS receiver works really well with collector, giving the sub-meter accuracy we were hoping for.
One issue we're having is that the accuracy indicator when collecting features through the app shows the value for the internal GPS, rather than the external receiver we're using, so there's not currently an indication of how accurate the points plotted are. The UK distributor for Geneq tells me that Geneq are in the process of releasing an app which compares the accuracy of an external receiver with that of the internal receiver, and so flicking back and forth between the two apps might give more of an indication of accuracy. Having the external GPS receiver accuracy displayed through the app would be the ideal situation.
Gareth