yes I would like that also.
The first step would be to get a DVB-T stick working.
One of the smallest is also supposed to have "Very low power consumption" according to the site: the PCTV Picostick
Picostick
Don't know if it is low enough to work with 200mA limitation.

I have one and it is working perfectly fine on Ubuntu using the driver and firmware found in this location:
Kernellabs Picostick V4L driver and firmware

I use the picostick with my netbook running linux Mint to watch Digitenne channels (a conax encrypted paid tv service in the Netherlands over DVB-T). I use my digitenne smartcard in a smargo smartreader+ using OScam as a key server, TVheadend as the decryption software and xbmc as the player.
It works pretty well, but the reception of the picostick isn't great when inside buildings using the small antenna connected directly to the USB adapter. (the officially supported Anysee E30 plus dvbt receiver only support the cardreader in windows, this is my linux supported alternative )

I would love to get the picostick working on the N900! But getting the other software to run on the n900 in order to watch encrypted DVBT broadcasts would seem a long way off.