Audiobooks are a tricky proposition for the subject of German unification. Most audiobooks cater to the popular history market and in the case of German history that means the Nazis dominate. There are a few exceptions though. Audible has an audiobook of David Wetzel's A Duel of Giants: Bismarck, Napoleon III, and the Origins of the Franco-Prussian War, which is a somewhat recent diplomatic history of the war. There is also an audiobook of Christopher Clark's grand synthesis of Prussian history, Iron Kingdom, which includes a chunk on the Prussian-led unifications. Audible also has a Jonathan Steinberg lecture on Bismarck, but to be honest, you're probably better off with the longer interview with Steinberg conducted by the New Books in History podcast. But these audiobooks are more the exception than the rule.

A better option for learning about history on the go is likely through a guided consumption of various podcasts on this topic. The New Books in History does not have one on German unification per se, but they do have a number of interviews on specialist topics that fill in the context of the events of 1871. Both Backdoor Broadcasting and the London School of Economics have podcast of lectures that typically look at German unification from a long-term perspective (warning- the search function on these two websites is atrocious, but worthwhile when you find something). BBC 4's In Our Time regularly features roundtable podcasts with historians, such as this Bismarck one, and other topics related to this period, such as a short discussion of Garibaldi or the 1848 Revolutions.