Ore Sniffer Mod 1.7.10 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 Ore Sniffer Mod 1.7.10
Download Links for Ore Sniffer Mod 1.7.10
For Minecraft 1.7.10