This is a pretty amazing excursion right here.
From the site: Leave the 21st century behind and revisit the Africa of the explorers! Join legendary safari guru Iain Allan, our right-hand man in Kenya, on an 11-day, 110-mile game tracking walk across the wilderness landscapes of Tsavo, Africa's largest national park. On this epic journey, you'll retrace the path of one of Iain's greatest adventures, undertaken in 1997: a "Summit to Sea" trek from the summit of Kilimanjaro to the beaches of the Indian Ocean (the expedition was later recounted in the book The Shadow of Kilimanjaro, written by Rick Ridgeway, a member of that original expedition).
I strongly advise you to check out the pictures on their site. Wow.