Those hand crank dynamo flashlights are not very bright. It would be adequate as a "be seen" light only.
You might consider a DIY dynamo LED lighting system. Here is a simple way to do it.
The 4 Ni-MH batteries will power both the headlight and taillight for a couple of hours with the dynamo disengaged from the tire or if your using a hub dynamo use switch S2 to disconnect the hub from the batteries. With the dynamo engaged 500mA is feeding the batteries and LED's. The headlight 1-watt LED consumes 350mA, 36mA is being consumed by the taillight LED, with 114mA being sunk by the batteries allowing a very slow recharge. If you need to recharge your batteries faster due to extended stand times or very slow speeds due to traffic you can open S1 turning off the LED's and pump 500mA rapid recharging current into the batteries. If your commute does not have many stops you can overcharge your battery pack. Just disengage the dynamo and run on batteries only for a while to discharge them. If you deplete your batteries to the point they stop working at stops or very slow speed open S1 to prevent damage to the batteries and LED's. You can use an LED driver to do that for you automatically with a circuit like this circuit.
A very simple battery monitor can be made from a 741 op-amp. I wont go into it here, just go to this link.
http://www.reuk.co.uk/LM741-OpAmp-Voltage-Indicator.htm
If you use a TL082 chip with two OP-AMP's you can make both low and high level indicators on one chip!