You’ll need a pretty large battery for 1 hour. Here’s an example calculation.
Assume 4 T200 Thrusters running at 75% thrust (210 Watts each, 840 Watts total). In an hour, you will use 840 Watts * 1 hour = 840 Watt-hours of energy. Let’s round that up to 1000 Watt-hours to account for some margin and so we don’t completely discharge the batteries.
If you’re running 4s lithium polymer packs the voltage will be 14.8V and the total number of amp-hours required will be 1000 Wh / 14.8V = 68 Ah. That’s a large battery. Here’s a 10Ah battery that could be connected with seven batteries in parallel to provide 70 Ah. (http://www.hobbyking.com/hobbyking/store/_64438__Multistar_High_Capacity_4S_10000mAh_Multi_Rotor_Lipo_Pack_US_Warehouse.html)
We also have a battery guide and calculator on our documentation: http://docs.bluerobotics.com/battery/
For the reed switch, I would recommend using an Arduino microcontroller and measuring the reed switch. When it is connected, you can turn the thrusters on. I can describe that in more detail if you’d like.