When a players inventory is full ,where there mining it will say inventory full and I says that in a hologram and in a certain amount of ticks the hologram goes away but it does this if the players inventory is full. name inventoryfull and no perms.
so say my inventory is full when im mining In the area im mining will get an alert and its a hologram and it says inventory if full
hmm you can do it with command block, you can detect if someone have more than 10 blocks on the bottom (because the inventory is full) in a radius of 5 blocks and make a title and subtitle command (in 1.8) then he knows that and the Messages would be configurable and with Color code Support if you do it on the way like usually with command blocks