If you have been asked to monitor feeds and or nappies, then these apps may be useful.
The problem is that they are written without a thought as to how breastfeeding works. If you need to monitor bottle feeding, then it does make sense to note down how many ml or oz baby has taken. But for breastfeeding you do not have this information. So all of the apps (I don't know of any which work differently) ask you to monitor minutes breastfeeding instead.
This is confusing. It doesn't give you any useful information, because babies don't feed at some kind of uniform rate. A baby may be attached for ten minutes at one feed, and for sixty at another feed, and may receive the same volume of milk. This is because milk transfer speed can vary depending on how sleepy the baby is and how full your breasts are, but also because it's common for breastfed babies to pause and have little breaks throughout a feed, whereas sometimes they will just keep going until satisfied and then conk out. Or one baby may feed frequently whereas another has long gaps. Some babies have one side at each feed, others two, some three, many vary from feed to feed. The most likely scenario is that a breastfed baby, particularly a newborn, will feed with absolutely no discernible pattern at all. That's fine if you know this and expect this, and it really helps if you are not clock watching. If you are looking at an app which creates a chart for you of your baby's feeding patterns, then this lack of a pattern is extremely likely to cause anxiety or at least confusion and stress. New mums already struggle enough with the unpredictable nature of breastfeeding without it being highlighted by an app.
Then if you compare with your friends' feeding logs or Google how long a baby's feeds ought to be you'll end up in an even worse mess because this will just confuse matters even more.
Generally if you're breastfeeding and being asked to monitor feeds it's more a case of make sure you wake the baby if necessary and offer the breast at least every X hours. The length of the feed is not important. Having it suggested as something to monitor in an app suggests that it is important information that you should be paying attention to, which is a myth that is likely to be harmful towards breastfeeding by introducing doubt and confusion and a sense that you're getting things wrong, when really everything is perfectly fine and normal. Some (most?) apps don't even let you log breastfeeds at all without using the timer feature! Apps logging sleep and feeding become confusing if your baby has fallen asleep while feeding and is still latched on during sleep (this is very common).
New mums are already battling loads of myths and misinformation and unhelpful comments and such about breastfeeding. I really think the way these apps work add to this and that can be harmful.
I don't think any breastfeeding tracking app would be useful but at a push if somebody did want one, I'd say the useful things to note would be
Time of start of feed
Comfort for mum (any pain or weird or uncomfortable feelings)
Last boob used
Comfort for baby (whether they are settled, need winding, sick etc)
That's it really - no tracking of minutes spent per boob. That doesn't help anyone.
(Also ideally loads of good quality info about normal breastfed baby behaviour, patterns or lack of, info about safe cosleeping, latch tips and links to all the helplines etc! Well I can dream :o)
Maybe I should write my own app!