Hello,
Are there any taxi apps in Spain, I.e., Uber?
I think FreeNow is popular in both Barcelona and Madrid.
But it may vary from city to city.
You don't need them, in major cities (ie Barcelona) there are plenty of taxis all day long. In Barcelona over 12000. Just head to any major street and in a few minutes you'll see taxis passing by, just raise your hand to any taxi with the green pilot on the roof on, and it'll stop. Easy peasy. Btw, ALL TAXIS have the same fares as they're set by the Transport Authority at the beginning of the year. Taxis in Barcelona are unmissable as they're all painted black and yellow.
I should have been more specific. Will be in Sevilla, Granada and Bilbao.