Vnc doesn't use an internet connection, it uses a wlan network. In fact you connect to your pc using an ip like 192.168.1.x and doesn't require an internet connection. To make an app using wifi you (in general) need to use a socket udp or tcp connection over a lan network: when you're connected to your home router, which provides both access to internet and a wlan network, you're only using wifi and not an internet connection. Try again with a vnc client over wifi. Also, bluetooth range is really short (the old one which n900 has, not the new 2.0 or whatever it is).