Särmä TST Thermal Cloak

Jess on Endurance Room has a really nice review of the Särmä TST thermal cloak. This is a shelter/poncho/bivy/sleeping bag inspired by the Jerven bag. Check it out.

I have a Jerven Original and a Jerven Hunter (insulated). These things just plain work and I'd expect the Särmä version to work just as well. A few years ago I used the Original on an overnighter as my shelter.

Incidentally, this pitch worked for the clear night I had, but the trekking pole in the middle was annoying when I had to get up in the middle of the night to pee. It protected me nicely from the wind, however.

One improvement I see on the Särmä is that it has loops for tie-outs instead of the grommets on the Jervens.

The one thing you need to be aware of when using these as a bivy or sleeping bag is condensation. They are waterproof and not at all breathable, so you'll get condensation. You'll want to air them out after a night's sleep.

A less expensive alternative for those on a budge is the USGI casualty evacuation blanket, or a heavy duty space blanket. I've used one many times as a "taco" around a sleeping bag or poncho liner. The downside is that they are smaller than the Särmä cloak.