I thought so too, but the paper version apparently has a ridiculously high (user) error rate. When the failure mode is an extra human it might be a net win.
I feel like there's a better option, it has to be possible to improve the paper version, without adding a battery, LCD and a CPU.
TestBuddy
Would be a good add in for ovulation tracking apps.
Also, if you are a pregnancy test manufacturer, maybe you release this app so you can see what other tests people use; educate them on the error rates of competitors; and offer 1 click purchase of your products.