Android :: IOS / GPS Battery Draw?

I'm investigating the possiblity of writing an app for Android/iOS4/both that would use GPS in the background. I found the "Receiving Location Events in the Background" section of the iphone developer documentation, which recommends that I only register for "significant location change" events. I'm not aware of any such capability in the Android SDK, but it still seems like a good idea to do it this way if I can (so as not to drain the battery). My question is this: has anyone done any sort of benchmarking for this on and iPhone/Android phone? So far, I've seen a lot posts/documentation saying that listening for GPS events in the background is a VERY BAD THING and I should AVOID IT AT ALL COSTS, but I haven't been able to find any numbers for just how much power a background application listening on GPS changes would drain (i.e. % battery drain per time app is running in the background).

This information might be helpful for me (and possibly others too) because I might be able to poll less frequently or even register/unregister my GPS listener based on power drain. Essentially, I could try to put a ceiling on how much battery life my app could drain while in the background.