Mike - is there any timeframe for this year (ie. Q1, Q2, etc) when this functionality would be added? This is a critical component, especially for webmaps that use cached images. In the desktop product, the cached images still load when zoom in beyond the smallest scaled cache layer. However when looking at the webmap - especially through a webmap shared to the mobile android/iOS tools for ArcGIS Online, the GPS will zoom you in beyond the smallest map cache.
It would be very helpful to stop the zoom scale at the lowest scale of the webmap - essentially saying this is the best resolution on this webmap that you will see regardless of whether GPS is used or not.
This has a number of critical applications because any cached layers in ArcGIS Online for Organizations currently require users to build cache scales all the way to the lowest cache scale if/when viewed on the mobile app otherwise it disappears from the view.
I hope this helps / makes sense, but resolving this will be a critical component for encouraging people to build and/or use cached services.