"At a first glance, this paper felt like magic," says a reviewer quoted in Dave Levin's summary of the V-edge paper by Xu et al.
It's awesome that a novel and elegant technique for measuring the drain of smartphone batteries would be discovered by researchers in computer systems. (Game on, chemical and electrical engineers.)
One thing surprised me: Fengyan Xu's slides tell us that V-edge "Works on most phones." But the conference version of the paper says, "We conduct all experiments on a Nexus S smartphone running Android 4.0." (Sec. 8.1; some battery profiling was also done on Galaxy Nexus batteries.) The 4% figure for average difference seems to apply to the Nexus S specifically.
To what extent have these results been generalized (or can they be generalized) to more than one model of smartphone? This seems like such an exciting way to get more reliable per-program accounting of power usage for zillions of smartphone apps and users. App stores should report this information.