In my experience as a consultant, investor, and software developer, I've completed a variety of tasks. I've touched too many technologies to list in my resume, or even on this page. The below skills and tools are ones that seemed most relevant to my career. I don't claim expertise in all of them – just that I've used them at least for basic tasks.
iOS, iPadOS, watchOS, tvOS Development
Core Bluetooth: Bluetooth Low Energy (BLE)
UIKit: UICollectionView, UITableView, UIStackView, etc.