It says you get more Speed when you level, but I wasn't sure about leveling with RC's.....
Let's take the Power Anklet for this example.
>Promotes Speed gain on level up, but halves Speed stat in battle. Adds 4 Speed EVs whenever experience is gained in BATTLE, regardless of the Pokémon fought. Its effect is doubled by Pokérus.
Source: Bulbapedia/ Power Items