Peter, I too have the GNS 5870. Yes it is the one that you need to swipe to turn on/off however I haven't had the issue you mention about it turning on in my flight bag. It also comes with a cigarette USB charger which ive used successfully in charging/powering both the 5870 and the iPad or iPhone. Obviously using the appropriate cable.
I've been completely satisfied with it however on comparing specs the XGPS model appears to be 64 channel whereas the 5870 appears to be a 32 channel version. Further looking into the theroy it shouldn't make any difference for our application, having a higher channel sensitivity will probably assist in holding a signal under cover.
I have the standard wifi only IPad 2.