This switched JST connector is the best way to quickly prototype with LiPoly batteries. On Adafruit paired a genuine JST connector with a slide switch that can do up to 600mA. Both are soldered onto a breadboard-friendly breakout. There's two ground pins, one 'switched' power pin, and one pin that is always on. This is compatible with the "JST PH 2-pin" connectors that are use in battery packs. Mates perfectly with all 1-cell LiPoly and LiIon batteries as well as 6V coin cell holder and 3xAAA battery pack. With this connector also mate the simple JST pigtails.