I've got a great chocolate stout on a nitro tap and I wanted to know it was possible to bottle some of it before the keg runs dry. The pressure is set to 35 psi.
You can't really get the nitro effect in the bottle unless you use a widget (Guinness) or use whatever top secret process Left Hand is using for their Nitro Milk Stout (I'm guessing something involving liquid nitrogen). Left Hand also uses pretty heavy duty bottles, probably because the internal pressure gets real high.
Since nitrogen is almost insoluble in water, you probably won't be trapping much in the bottle. You should be fine in that regard. Keeping the CO2 in there is a different story, maybe check out the "we don't need no stinkin bottling gun" thread for some ideas. I'm guessing you'll need to turn the pressure way down and use a normal faucet (if you're using a restrictor faucet now).