I got my Nexus One today, and turned on the WiFi HotSpot feature, resulting me to have Nintendo WiFi Connection.
It’s even very fast, for a smartphone.
It’s a Nexus One and DS are a really good combo, although you’re not allowed to use WPA2 (no WEP), because it won’t work on the DS.
At the Google side
1. Go to Menu > Settings > Wireless and network settings > Tethering and portable Hotspot. (Note, I have a Dutch Nexus One, so it’ll differ in your language.
2. Select “Portable WiFi Hotspot” and tap “Settings for portable WiFi Hotspot”.
3. Select “Portable WiFi Hotspot” (again) and tap “Configure WiFi Hotspot”
4. Give it a name you like, and choose “Open” (important, because the DS (Lite) doesn’t understand WPA2).
At the Nintendo side
5. Access a random WiFi enabled game and go to the WiFi Settings.
6. Go to WiFi Settings > One of the three spaces > Access Point.
7. Now select our Portable WiFi Hotspot, and press A.
8. Now go play through the internet, wherever you like.
Note: This connection was made using 3G, on Vodafone NL’s network, with a PrePaid thing + Endless Internet.
Speed differs from provider to provider, from phone to phone, and maybe WiFi could be faster.