Is the display on a handheld large enough to be useful for programming? Studies show that larger monitors increase programmer productivity. It seems reasonable

Is the display on a handheld large enough to be useful for programming? Studies show that larger monitors increase programmer productivity. It seems reasonable to conclude that a smaller monitor would decrease it even more significantly. An iPhone screen (320x480) is similar to what the Mac Plus had (512x342), but it subtends a much smaller angle of your field of view. Perhaps the appropriate measure is in square "characters". The VT100 is probably the bare minimum -- 80x40 characters, or 3200 characters square. There's no way the iPhone can display that legibly. Not saying the idea is impossible, but this is definitely a problem to overcome, either through hardware (HUDs in special wearable glasses? Big lenses to enlarge monitor size, like the movie Brazil?) or software (some other method of input?)