Proper Wudhu is valid no matter what you think about during performing it, though it is recommended to recite Sura Al-Qadr during performing Wudhu as well as special supplications of Wudhu which are mentioned in our books of jurisprudence.
'Prayers need to keep your heart in your Prayer and not out of it. Prayer is valid even if you think about unrelated things, but the reward of the Prayer is more when your heart is in the Prayer. Allah Says in Quran: They have won indeed, the believers who are dedicated in the Prayers. (Sura Al-Mominoon, verses 1 and 2)
Wassalam.