Yes, I use the Windows Phone version and love it. It is based on the TFP method.
(Disclaimer: my buddy (and fellow Aggie) wrote this app so please let me know if you have any feedback that you want me to share with him.)
Yes, sounds like a great time to switch. I admit the first time I dumped normal household bleach (fragrance free) into my pool it felt "off" to me. But I was amazed at how effective and easy it was...I recommend you give it a go.
I also recommend the TF 100...better bang for your buck. I like to use FAS/DPD and OTO but I am not a fan of tablets. (FWIW I maintain a similar pool to yours and switched it to salt water and have never looked back.)
An old college buddy of mine just showed me the one he uses (I think his company may have developed it.) It is on all 3 app stores:
http://www.cambiumtechnologies.com/poolcalc.html
There is finally an app that supports all 3 phone operating systems...iOS, Android, AND Windows Phone.
http://www.cambiumtechnologies.com/poolcalc.html