If you use one of the main rostering systems such as AIMS/ecrew (they support others) then you don't actually need to bother keeping track each leg with an app on your phone although they do have one for both IOS and Android. The PC/Mac based application takes your airlines rostering log on details and you can download all of the historical flight details whenever it suits - reg, a/c type, block times plus it will calculate day/night. All you would need to do is to edit the flights to keep track of landings, approaches, P1/P2, PF/PM, remarks etc. There are various print format options if you want a hard copy.