thank you for an idea. Honestly, we're currently working on implementation of such feature. So at this moment isn't possible to record Z coordinate (altitude) but it'll be available probably in next month.
I found this old topic and I'd like to say that this feature is already implemented in LocusGIS. There is an attribute type "Feature properties" (Layer > settings > attributes > PLUS > Feature properties). With this attribute it's possible to record X, Y coordinates, Elevation (Z coordinate) and accuracy values.
When I record a point and when I select it I have no Z information.
Where can I get it ? Can you display it with the X/Y information ?
Is it possible to add an option to add Z as attribute (and also X,Y) ?