I completely agree with this, and am a bit disappointed that this post is 2 years old and the idea not implemented yet.
It would be great if Wemo allowed for more information to be sent to IFTT than just switch and time for the standby mode entered trigger. Duration for the last run would be helpful, but also more information about power usage.
I know data can be exported from the Wemo app, but that doesn't lend itself well to automation.
I don't see belkin adding this function very soon. FWIW you can use AutomationManager to do the Drive logging using the WemoOnDrive extension.
It will log all wemo state changes and insight power measurements to a drive sheet (it handles a few other device types as well). From there it becomes a case of using the right formula or script to pull, filter, or calculate the desired data. Google sheets is really quite powerful, and it's possible to drive a lot of automation either via AutomationManager or google sheets.
For example I create a second sheet and use a formula to filter/populate it with the subset of the full dataset:
=filter(Sheet1!A2, Sheet1!B2:B = "QuadPlug_T", Sheet1!D2 = "on")
which grabs all of the log/temperature entries of that device when it's "on" (vs offline). (My insight isn't doing anything right now so it'd be a flat graph, for it you'd use "on" and/or "standby").
From there I can easily produce a graph showing room temperature today using google's tools: