There are some great kindle, android and ios apps out there for learning!   I've also listed some of my favorite multi-sensory programs and resources that work well for our students and are worth the investment.  Here are just a few suggestions:
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Abby Sight Words Games & Flash Cards for Reading Success.  There is a free and paid version.  Android and iOS.
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More resources on the app.  For Kindle, Android, and iOS
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Teachly: Addimal Adventures.  Free and paid versions.  Single digit addition, multiple strategies
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Not an app, but multi-sensory learning package to learn to spell Letters & Sounds, Colors & Shapes, Numbers, Math, Sight Words, CVC & Word Family Songs, Phonics.
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Touch Math is a fantastic method that works for many of our students.  The touchscreen apps are the best way to learn this system.
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Child 1st offers a number of learning products.  I really like the Snapwords product which offers visual and whoie body strategies to learn site words and more.  They also have apps for this. 
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Sight Words that stick is a favorite teaching tool.
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I See, I Spell, I Learn is one of my favorite sight word products.