but the idea would be some service/website/app where I could put all my wallets at once to track them, the balance and notify me of any transaction/movement
The apps I suggested above should do that and more. BlueWallet as suggested by Zaguru12 should also do that. You can import the master public key of your wallet, and it will notify you whenever there is an incoming transaction in any of your wallet's addresses. You should also be able to import multiple wallets, and not just one.