Auto-WiFI
/Some iPhone competitors offer a clever feature for conserving battery life: They use geolocation to figure out where you are, automatically enabling and disabling the Wi-Fi antenna when you’re away from a known hotspot.
That does sound like it could be great (not that I've ever felt like my batter life is lacking), but I'd need to have fast access to turn WiFi back on if I was near a hot-spot my phone didn't know about. In fact, quick access to WiFi, Bluetooth, 3G, etc should be baked into iOS. I'd rather see that than Lex's suggestion.
(Via The Brooks Review)