Spawn a chest upon death containing all your stuff.
The chest can be mined but not destroyed in any other way.
Mining the chest will however not give you a chest back.

Changelog

0.13.3

• Updated for Factorio 0.14.x

0.13.1

• Blueprints book will now retain the blueprints upon death.
• A pistol and 10 regular magazines in the gun/ammo slots will be removed from the death chest since you get them back when you re-spawn.

0.13.2

• Fixed a bug where spawning a death chest in a tank would cause an error.