Interesting web site. Summarizes omoto in understandable terms.
Za-zen is mentioned from time to time with aikido, but as it is stationary and usually done for long times, it probably doesn't fit into many people's time frame for aikido practice.
I've read of people doing something similar in Hawaii in the ki schools, which they call "breathing," where they meet specifically for that, sit in zazen, breath in and out while someone rings a bell over and over. It's supposed to build physical strength and ki from what I understand. PErhaps on some of the aikido pages for schools on Maui you could find more, specifically the Shinichi Suzuki school at Wailuku, Good luck.