The Idea is fantastic for some very simple reasons:
The implementation could be done so it uses up quite a few batteries, giving out coordinates for a survivor who has no idea where he is relative to other things is quite hard after all and would take a lot of time to communicate. Also, it would need to be a random item, not a specific one, something in the direciton of ‘There is food stashed away at location x’x’x’. This gives the possibility of it being absolutely useless as well. Also, deciding on the quality of the item could be a valid option too, at least with a good downside to it. ‘There is a high tech gun there, but I couldn’t get it because the place was overrun, maybe you got more luck?’ And flavor text like this could be used, generally using a quest system like the one were a mother zombie is created, just with for instance a crate or locker with the items, and several mobs in the vicinity, from 2-3 normal zombies for crap up to shocker brutes mixed with hulks and other high end zombies swarming the place.
While it is not very useful for an advanced character besides the fun of it, it surely is good when in a pickle, but you’re never sure what you will get from your fellow ‘friends’ 
The biggest part of it all thought would be implemented cooldown, make it only available once every 10 days for instance and you have a perfect way for a twitch streamer to get the attention of their community, which in reaction would be a nice way to boost the popularity of the game, interactive game mechanics are always a blast as seen with quite a few other titles. It opens up a lot of possibilities while having no downsides with proper implementation, or at least none I could think up, the word is ‘proper implementation’ as it can easily ruin the balance otherwise.