Just a quick post about a mechanic that I've been playing with for awhile. I really like the effect it gives upon the game, and have been using in game with for over a year. It all started with the Hourglass of Respite, a fan created magic item I found on EnWorld back in November of 2014.

Hourglass of Respite
Wondrous Item, Rare
Once per day this hourglass can be activated by saying a command word and starting the sand flowing and anyone who rests for two minutes while within thirty feet of it, recovers as if they had spent an hour resting thus getting all the benefits of a short rest.

I gave it my Age of Worms group fairly early, but have since changed it from being the effect of a magic item, to being a resource that the party to use, once per long rest, that I call a "Quick Rest".

Quick Rest

A quick rest is a period of downtime, at least 2 minutes long, during which a character catches their breath. The character does nothing more strenuous than eating, drinking, reading, and tending to wounds. A character can spend up to half their level (rounded down) in Hit Dice at the end of a quick rest. For each Hit Die spent in this way, the player rolls the die and adds the character’s Constitution modifier to it. The character regains hit points equal to the total. The player can decide to spend an additional Hit Die after each roll.

A character can’t benefit from more than one quick rest until they have taken a long rest.

A character regains some spent Hit Dice upon finishing a long rest, as explained below.

So far it has been a carefully used resource. Usually saved until right before they suspect a "big fight", or after a particularly tough fight but they want to move on quickly from, like when they are racing against the clock. There have been several times when it hasn't been used at all.

Getting to use it only once between long rests makes it valuable, and has made them carefully decide when to use it. Only getting to spend up to half of their Hit Dice during a quick rest I feel balances it against it only taking up two minutes.

Most of the text is copy and pasted straight from the rules for a short rest, with only a few changes. I keep it listed in with all the rules for rests, hence the reference to the "long rest, as explained below".