Finding a clear signature of topological superconductivity in transport experiments is an outstanding challenge. In this talk, I will discuss the possibility of exploiting the unique properties of three-dimensional topological insulator nano-wires in order to form a tunable setup for realizing topological superconductivity and observing it in transport. This is achieved by inducing superconductivity in half of the wire, which can be tuned at will from trivial to topological with a parallel magnetic field, combined with a perpendicular field generating chiral modes in the normal part of the wire. In the single mode regime, the conductance is quantized at 0 or 2 (in units of the conductance quantum) indicating trivial vs topological superconductivity. I will show that our proposal may be intuitively understood as a variant of a Majorana interferometer, and discuss robustness to disorder and finite temperatures.