Don't know the answer to your question but, having a Wifi application I needed to keep the battery life as long as possible.
What I've done is to change the Wifi battery mode (CAM ==> Fast or the other one) ==> really improve the battery life (at least, enough for the use in my case)
Maybe could be a solution without doing weird stuff !
In my application, I am configured in Best Power save mode for the wifi and, don't know what really is the difference with CAM mode but:
Notification works great (even when SB1 is in "sleeping" mode)
Push to talk answers as fast as I press the button
I'm not a wireless expert, but here's a posting that explains the Max power save.
This could add up to a 1 second delay in receiving a push to talk message (or other IP packets) but once the radio is aware that there are packets coming, it stays awake until it is done processing them. So for Push to talk, it may be acceptable, and it will save a lot on battery life. I think that the Fast Power save mode is similar, but it wakes every 3 beacon intervals. CAM mode never shuts off the radio, it is always listening (and consuming power).
Also note that the DTIM setting on the AP will have an effect. We used to set this at 10 as a default on our APs for data only apps, I think we now typically use 2.
In most cases, the above works fine, but I have seen times where the power save modes don't seem to get along well with the AP. Sometimes this can be a setting in the AP that needs to be adjusted.