LootSpec Switcher displays a simple bar with all your specs on it and emphasizes the one matching your current loot specialization. You can click on icons to quickly switch loot specialization.
You can unlock / lock the addon with the /lss chat command.
This addon is also a more visible indicator of your current loot spec in case you forget to set it to the correct value. Winning heroic retribution bonus rolls as holy paladin after a LFR run is not fun !