Bringing a small camping stove makes hot, cooked meals easy enough in the outdoors. If you want the most convenient cooking device for camping, though, we doubt there's anything better than the Trekmates Flameless Cook System.
That's right -- cooking without flames. And, no, it doesn't involve an electric cooker like you have at home (because, you know, there's no wall outlet in the wild). Instead, it uses chemical heating packets that lets you cook food without having to start a fire.
The Trekmates Flameless Cook System is a self-contained cooking unit that can be used to heat up both wet and dry foods. It comes in two varieties: an 850 ml Cook Box (for heating food) and a 360 ml Cook Flask (for heating water). Heating is provided by disposable chemical packets that come in either 20g (High Power) or 50g (Super Power) quantities. When immersed in water, the 50g version can reach 90°C in 15 minutes, providing that level of heat for 15 minutes straight before dying out.
Both feature a plastic outer container and a stainless steel inner container that can be separated before use. To use, just put the chemical heat packs onto the plastic container and add water to activate the heating elements; then, put your food or drink in the stainless steel compartment and set it inside the plastic rig. From there, you simply lock the lid and wait the prescribed time for your meal to finish (usually 7 to 10 minutes).
Since you'll have to use up a packet every time you cook anything, this probably won't be cheaper than a regular portable stove. However, the flameless capability means you can do your cooking inside a tent or even in the middle of a rainstorm. Price is £30 for the Cook Box and £20 for the Cook Flask (both with several heat packs included). Five extra heat packs will cost you £10.