Before we’re actively replacing mitochondria within living cells, we may use more conventional targeting techniques to guide small molecules or even protein complexes directly to the mitochondria. Hoye et al. describe new tools based on conjugating interesting molecules to gramicidin (remember, mitochondria are distantly related to bacteria) or lipophilic compounds that preferentially partition into the mitochondrial membrane — perhaps thereby allowing repair in situ.
Keeping mitochondria properly tuned is essential to prevent broad-spectrum oxidative damage but also a variety of age-related diseases (q.v. this paper from Civitarese and Ravussin, which describes the relationship between insulin-resistant diabetes and certain ultrastructural abnormalities of the mitochondria).