[Most of this discussion is moot but I'm posting it in case it'll help other users.]

Thanks, I know that one. My object is to leave mobile data enabled while making sure my apps don't use data behind my back. My version of Android (4.1.2) has quite a nice "Data usage" page in system settings, which includes "Set mobile data limit" and "Alert me about data usage" options along with a graphic display of how much data each app has used during a selectable time window. So my question is really seeking advice from people who have already run under an expensive data plan.

For example, my current "Data usage" for Jul 28-Aug 4 shows this:

• Android OS 11.65MB
• Maps 7.59MB
• Google Search 3.86MB
• Chrome 2.09MB
• Google Play Store 1.98MB
• xScope Pro 1.72MB
• Facebook 1.23MB
• SmartActions 293KB
• Motorola Services 207KB
• SwiftKey 143KB
• Skype 138KB
• RATP 94.01KB
• Verizon Message 39.43KB
• K-9 Mail 25.10KB
• Etc.

RATP is the Paris-area transit system's app, which is the one app I will certainly be willing to spend a few euros on if need be while in Paris. I can try to remember not to use other data-consuming apps, but it'd be ideal if I could find ... uh, what I just found on the Google Play market: a data enabler widget.

Thanks for your reply, I'll leave this message in case other users find it useful. I'm just going to put the data enable widget on my desktop as a convenient way to turn on data when I want to use it. In summary, here's my strategy:

• Disable sync
• Install data enable widget
• Keep data disabled except immediately before and after I need a bit