These appeared on my rims after taking my bike to a repair shop. Does anyone know what these are and how to remove them?
Those are wheel weights. They are to balance out imperfections in the weight of the tire to avoid vibration at speed. I would recommend not removing them. If you're concerned about them standing out against the tire, you can remove them carefully with a flathead screwdriver, scrub off the remaining adhesive, and replace them in exactly the same spot with exactly the same number of weights of the same weight per weight of a different color (i.e. black) or paint them.
They are wheel weights, and are usually divided between both sides of the wheel.
A wheel assembly can be unbalanced in more than one plane, and modern digital balancing machines take this into consideration and indicate the amount of weight and the placement of each weight on the wheel. The weights are not always at the exact center of imbalance, but divided equally, both radially and tangentially, to each side of the lightest point on the wheel. This gives better results than a single-point weight of a larger size. They are stick-on to prevent damage to the rim.
Simply paint them to match the rim. No one will notice when the wheel is in motion anyway.
Of course,the NSA could be tracking you! ;)