They have an app version available for 99¢ if anyone would like to support the developer! Everything is available in the free version, so you won't get anything extra if you buy it, and you aren't missing out on anything if you don't. I think it's super cool that they have all these helpful tools available for free and I hope more people who are able buy the app version to support them.
I have a few dollars kicking around in my Google Play Store account from taking Google Rewards surveys, and I like to use it to support devs, so I jumped right on it!
I'm hoping maybe having it installed as an app and on my phone screen home page thingy will help me be less likely to forget about it again and hopefully be more likely to actually think of using it when I need it. Any time I remember it exists, I can't think of anything specific to use it for...any time I actually need something like it, I forget it exists. 🙃 Curse this damn brain!!
Also, like others have said, they have a handful of other great tools on there. Click the little menu thingy in the top left corner and you can look through the other tools and get a link to the appropriate app store to buy the app and help out the awesome person who provides these helpful, life changing tools for free!