WizKey is described as 'makes it easy to type accented and other special Unicode characters using a standard US/UK keyboard with easy to remember keyboard shortcuts' and is an app in the OS & Utilities category. There are more than 10 alternatives to WizKey for a variety of platforms, including Windows, Mac, iPhone, BSD and PortableApps.com. The best alternative is BabelMap, which is free. Other great apps like WizKey are Character Map (Free), WinCompose (Free, Open Source), Rocket (Freemium) and PopChar (Paid).
BabelMap is a free character map application for Windows that allows you to browse through the entire Unicode character repertoire of over 107,000 characters, or search for a particular character by name or by code point.
The character map that works! PopChar is an application that lets you insert special characters, umlauts and foreign letters into any document. With this character map, there is no need to search for or remember complex keystrokes.