Camera Batteries for headlamps

I am sure other people have used this idea, but I have never seen it posted.
I have found 7.4V li-ion SLR camera batteries excellent for my Stenlight and I think they could be usefully in many home made lights as well as some modified commercial designs (I seem to remember a post that said the Apex was fine with 7.4V)
The advantage compared to other Li-Ion battery packs is that they can be found very cheep. Digital cameras are progressing rapidly and batteries are often specific for one Model and retailers will sell them off when the model is no longer popular. I picked up some 7.4V 1600mAhr packs for $1 Australian. So far they are still fine after about 300 cycles.
They also come with a hard plastic case giving some protection to the cells and copper tags that are safer to solder.
Rember Li-Ion packs can be dangerous and it is hard to know if the packs are protected (I suspect most are). You need something like an RC charger to charge them.

I've had similar thoughts about the Black & Decker VPX battery system or other Li-ion powered portable tools. I think the VPX pack uses 2xA123 for ~7 watt hours. The pack is a nice shape for a pocket or maybe headband.

Many of them have standard size cells inside. For example 16340. I have cannibalized a few old packs and are using the cells in flashlights.

I've converted a River Rock headlamp (6V with 2 CR123) to work with a Black and Decker VPX battery.

The advantage of this approach is that I can still use the VPX charger without worry about safety issues.

The modification also allows me to work with a 4 AA battery holder from Radio Shack (enclosed with a small switch) so I can switch between these two power sources.

The only issue might be the weight. 4 AA batteries on the back on my head tend to be a little heavy.