One of the few frustrations that I have using this service, is the instability of the approach sequence. The HSI continuously switches between airports and approaches.
It should be fairly straightforward Kham in the mapping function, to select an approach at the destination airport. The same function could also allow a pilot to choose a SID or STAR in future versions.
In the meantime, it could be easily improved by allowing the pilot to lock in an approach, once it appears in the HSI. This could be done by simply allowing the pilot to tap The HSI, whereupon the word locked would appear underneath the approach information on the right.
Since the approach information is already embedded within the app, allowing pilots to cycle should be easy.