What type of monitoring are you referring to?
If it's just contraction timing, there are tons of apps, and it's probably the easiest way to do it.
If you're talking about the keeping track of diapers and feedings etc etc ... I think all that accounting drives you crazy and is not worth it. If you ave an issue because of which you need to do it (jaundice, excessive weight loss, etc) then it's worth doing on paper (one at the changing table, another wherever nursing happens) so that no one forgets to write it down. And then just stop once it's no longer needed.
If you're talking about fetal heart tone monitoring during labor .... I don't think that's something you can track through an app. Either doppler / fetoscope + charting (excel?), or the big hospital machines and the strip they generate.