The Ore Sniffer is a block that scans the area around it and marks the ore and minerals for you. When you place it down, it scans a 13x13x13 area around it. You can also configure what to display when you right click on the Ore Sniffer. (Toggle the ores/materials on and off, as well as distance). Everything should work fine on SMP.
How to install:
- Download and install Minecraft Forge.
- Download the mod.
- Go to %appdata%.
- Go to .minecraft/mods folder.
- Drag and drop the downloaded jar (zip) file into it.
- If one does not exist you can create one.
- Enjoy the mod.