To be more technically correct the signal coming out of the N900 is an analogue PAL or NTSC signal.

Translating this to a digital resolution is not as simple as saying it is 702x576

for vertical the number of lines is exactly 625 for PAL and 525 for NTSC but since TV's only display 576 and 486 respectively only these lines will have the video signal.

For horizontal it is even more complicated - yes internaly the N900 may or may not create the picture using 702 or 720 pixels, but the signal coming out is analogue and hence really has infinite number of horizontal pixels, the way the receiving TV samples this analogue signal will determine the final number of pixels displayed.

But back on topic, the N900 signal is compisite video - for VGA you need an RGB signal. There are plenty of composite to VGA converters on the market.