You can with a 3G + Data Plan iPad 2 / iPhone and above.
Create a Personal Hotspot wifi with a certain name and password.
Have the Apple TV connect to it.
Now take you Apple TV anywhere with you.
To setup an airplay/projector broadcast.
Start the Personal Hotspot wifi.
Connect the Apple TV to any hdmi projector.
Done. You can airplay your keynote or video to the projector.
NEXT...
This will work with any AirPlay enabled app. Using Keynote with AirPlay is no different.
Tap Keynote to launch it on the iPad, and then open the presentation you want to give.
Double tap the Home button on the iPad itself, and the multitasking bar will appear at the bottom of the screen.
Swipe to the right to reveal the media bar, which has the AirPlay button just to the left of the Volume slider.
Tap the AirPlay button and select Apple TV, then tap the Mirroring switch to turn that on. The TV screen should now have your presentation on it, ready to go.
You can also use this method to send the signal from any AirPlay enabled app video-out to an AppleTV.
Enjoy a "walk around, ipad in hand" wireless presentation.
PS. There are also some older VGA projectors, for those you might need an hdmi to vga "active" converter cable to hook the apple tv to it. Haven't tested this, and that cable is around 40-50$.
I'm not aware of a jailbreak that forces only a VPN and the core OS has no provision to only route traffic through a VPN.
The OS needs to contact an insecure network and send traffic in order to establish a VPN connection. For the time the device is connected to the network and not having built a secure tunnel - you are vulnerable to network sniffing. Even once you have a VPN - the traffic can still be sniffed and recorded for later analysis, but the encryption/obfuscation makes it harder to tell what data is being transmitted and to what servers you are communicating since all traffic goes to the VPN server.
In short, you need to be vigilant to ensure the VPN reconnects. If you make sure that your iOS device does not auto-join these untrusted WiFi hotspots, you will have to manually re-join if it drops so that you can manually fire up the VPN again and the device will not inadvertently re-join and put your traffic and data at risk.
Best Answer
it is possible to do it through bluetooth, dock connector, and 3.5mm headphone jack!
in order to use it though wifi you need a compatible application and i have never heard of such thing! after a little goggling all i found was bluetooth connected ones, because it offers a P2P connection witch is much more reliable!
(sidenote) mics though wifi routers could, be unreliable, specially in poor connection!
however there are mic's that include a dock connector dongle for a stable P2P connection something like this