Mathieu Martyn

UX Design

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TU Go 2.0

TU Go is a ground-breaking multi-platform service that makes your phone number available over Wi-Fi, keeping users connected in poor signal areas, helping them avoid roaming charges when abroad and supporting use of other devices without SIMs such as tablets or PCs to call and text, all using their existing Telefonica phone numbers. TU Go has been available in the UK since 2013, has since gone live in Argentina, Peru, Brazil, Colombia and currently has well over 1M registered users on iOS, Android, Windows Phone 8, Windows PC and Web.


  • Role: Lead UX Designer
  • For: Telefonica
  • Timeline: 2013 - 17
When I joined the project team as UX Lead, TU Go presented an event-based timeline to users, with tabs for each communication type - calls, messages and voicemails. This was a system-focused, impersonal and dated way to display what is very personal content. No threading meant users could not see any continuity in conversation, and spreading communication with someone across the tabs made for a lot of unecessary navigation. I led the design work to introduce threaded conversations, integrating all communication types into a single thread per number.


This included:

Redesign of the app architecture for each platform, greatly simplifying the interaction model and reducing navigation overhead.

TU Go 2.0 Android Architecture
Detailed specification for iPhone, iPad, Android phone and tablet for development and test teams in Spain and Israel.

A TU Go 2.0 spec sample
...having to use a pre-existing in-house template resulted in enormous documents with a convoluted creation workflow that didn't make things easy for anyone. I used a simpler and more effective approach to specification for development later in the project.
Frequent user tests across platforms was part of the natural rhythm of the project - here using the services of an Android developer to create and test a native Android prototype.

User Testing TU Go 2.0 for Android
Working closely with a UI designer we developed a coherent cross-platform visual identity for the service and a framework to accommodate Telefonica sub-brands in different markets - O2 in the UK and Movistar and Vivo in Latin America - with their different identites and colour schemes.

Project 01a
Once the app framework was in place, I switched the team over to creating simpler deliverables - use-case based flows. These were quicker to produce, easier to maintain and gave a much clearer idea of the interaction flow. Most importantly, they were also clearer and easier for developers to consume. This led to the developed service being much closer to what had been specified than was previously the case.

iOS Flow
Since the first release of the 2.0 version to app stores in August 2014, I led the team in continuously designing and delivering new features and enhancements updates to keep up with OS versions, working closely with developers and visual designers. Feature updates have included Group chat, Media sharing and Video calling (Android and Web only). The iOS and Android clients average 4 stars on the App Store and Google Play.

TU Go service was discontinued at the end of 2017, replaced by native Wi-Fi calling.