Hotpatching is a really cool technology. Being involved in that realm, here are the most notable hotpatching solutions.
List of commercial hotpatching solutions
Apptimize has a product to hotfix errors, called “Instant Update”
Rollout does hotpatching for iOS.
Hansel focuses on mobile Java applications.
Makitoo provides a hotpatching technology for Java (Android and server applications)
List of open-source solutions
JSpatch bridges Objective-C and Javascript using the Objective-C runtime so as to write hotfixes in JS.
Nuwa provides a framework to support dynamic patches in Android.
tinker is a hot-fix solution library for Android, it supports dex, library and resources update without reinstall apk.