Cant get my iMac to wake up with my iPad or ATV2

I have a 27" iMac, Wi-Fi iPad and Apple tv 2

I can managed to stream movies and music from my iMac to the Apple tv no problem and the iPad remote app works wonders. My only problem is that when the iMac goes to sleep I cant get it to wake up without going to the computer and doing it manually, I have checked that wake on demand is checked in energy preferencese but no matter what I do I cant get my iMac to wake up when I use either the iPad or the Apple tv.

Is there something im missing?

I have my ATV connected via ethernet to my router and the iPad and iMac are connected via Wi-Fi.

I have a Sky supplied router, I belive its a netgear.