Every time I signed up for WW, I had the same idea. Quit after the three month special and just use other tools. The problem was I found it so tedious without the app that I would start to slide back to old habits.
I hope you find something that works, but this time, I'm going to stick with the WW app. I'm also feel like if I'm using the intellectual property and the information created by WW that I am obligated to pay for it. Using another app that simulates or outright rips off WW seems fraudulent but I'm an artist so I'm very concerned with those types of things