In my humble opinion, to study functional genomics in vivo, the best would be to place your reporter gene into humanized animals (i.e. making transgenic reporter-humanized mice). Pronuclear DNA micro-injection in the oocyte is the most frequently used technique for generating transgenic mice; unfortunately, pronuclear transfer is expensive, labor-intensive, time-consuming and require coordination of many experimental steps, so personally I feel an urgent need to alternate, cost-effective and more rapid approach to obtain desired transgenic founders.
Recently, I have been occasion to wonder about a male-driven transgenesis approach, and I found interesting literature. Here a few references (feel free to comment missing items).
Suveera Dhup, Subeer S Majumdar (2008). Transgenesis via permanent integration of genes in repopulating spermatogonial cells in vivo Nature Methods, 5 (7), 601-603 DOI: 10.1038/NMETH.1225
Chang KT, Takahashi M (1999). Production of Transgenic Rats and Mice by the Testis-Mediated Gene Transfer Journal of Reproduction and Development, 45 (1), 29-36
Maione B, Lavitrano M, Spafafora C, Kiessling AA (1998). Sperm-Mediated Gene Transfer in Mice Molecular Reproduction and Development, 50, 406-409