Music Stands: After just three days of practicing without a stand, habits are formed that can take months to fix. Music stands will both improve your child's playing AND make it more enjoyable to practice. Students should avoid putting their music on a piano as the height of a piano's music stand is incorrect for both sitting and standing to practice. As another note, students should never practice while sitting on their beds.
Tuners: Tuners are a phenomenal tool that students should get used to using early. A physical tuner will be great but students will find that the free version of the Bandmate Chromatic Tuner will be excellent for their early development (for Android, Apple, and Kindle devices).
Bandmate Chromatic Tuner
Metronome: A metronome is a tool used to improve a musician's time and rhythm. These are also available on the internet as well as from Graner and Meeker Music. Metronome Apps are also available. I personally like the "Metronomics" app as it gives options for creating fun rhythms. "Musicians Kit" app also supplies a good metronome as well as a tuner and recorder in the app. Metronomes should be used for most of the practice time. Encourage correct foot tapping as well as counting to improve a sense of beat and rhythm.