iOS 4.2.1 seems to support this "Network Controlled Fast Dormancy" for saving battery in UMTS networks:
http://blogs.nokiasiemensnetworks.co...e-performance/

iOS 4.2 supports new tech to reduce network congestion, Nokia Siemens says -- Engadget

heise online - UMTS-Verbesserungen in iOS 4.2

Wouldn't this be something for our small webOS-batteries too?