Cleaning Inside Washing Machine

It won't do any harm, although whether you need to use any regularly is another matter. Washing machine detergent already has anti limescale agents in it and as long as you use the correct dosage for the level of soiling and for the hardness of the water in your area you don't need any extra protection. For anyone in very hard water areas, who may be concerned about limescale the occasional use of limescale removing products may help but in theory it just isn't necessary. Some people who may still suffer from limescale effects in their washing machine are presumably constantly under dosing (which is very common because there's an urban myth that manufacturers of detergent tell us to use more than we need to) and so their washing machine's aren't fully protected.

Products such as Calgon don't do anything that proper high quality washing machine detergent doesn't do although they -

Help protect against under dosing

Soften the water allowing you to use the amount of detergent recommended for soft water in a hard water area

The last effect could potentially save money if the money saved by reducing the amount of washing detergent is greater than the cost of the Calgon (or similar) tablets. I don't know of anyone that's done the appropriate tests to determine this but Calgon claim you could save up to 25% of the amount of detergent required. 25% is presumably the best case scenario, it depends how much the tablets cost compared to how much you save in detergent, which may not be significant for the average washing machine user.

For (much more) detailed thoughts on the subjects raised here including recommendations regarding the "service" or "maintenance" wash at high temperatures read -

Causes of grease, slime and smells in washing machines

Hard water & limescale in washing machines

Finally, the product you mentioned is a limescale remover, which is obviously used if you already have limescale, whereas the ones I mentioned are limescale prevention products.