I was provided a gift code and invited to look at a TI-83/84 "Work-alike" clone, GraphnCalc83, for iOS. The app is a universal binary so it supports both the iPad and the iPhone/iPod. I'll be reviewing this app on an iPhone 6 on iOS8, I did use it on an iPad as well.
The Bottom Line The app is remarkable. The developer set out to create a graphing calculator for iOS that does its best to emulate TI-83 programs. While I can't recommend this app as a substitute for a physical calculator, due to the extreme differences and lack of complete support for TI-83+ programs. I can recommend this app to those that can't afford a graphing calculator and have a desire to learn coding but do have access to an iOS device like an iPod or iPad. I'd like to see iCloud integration to a degree, of course the more integrated the better but save/share and retrieve would suffice. The app doesn't even support "File Sharing" under iTunes, which means the only way to get your programs off and on your digital calc is to e-mail them. If File Sharing is supported, retrieving and sending programs would be as simple as dragging and dropping to/from the File Sharing window or clicking the appropriate buttons. If this application takes off it'd be amazing if we'd eventually see a centralized way to share programs with others similarly to ticalc.org.
In brief, it's not for everyone but for those with an iOS device and a need for a graphing calc with programming capabilities this is a must. You can check it out on the App Store here (USD $5.99).