Written about by others, specifically discussing using the sai when practising the karate kata niseshi (nijushi-ho), a good example of actually applying unarmed Okinawan kenpo (karate) forms to weapons or tools is in the Okinawan karate school called Isshin-ryu. You can watch Master Tatsuo Shimabuku demonstrate kusanku no sai. Essentially, any karate kata can be applied to at least one implement, though some fit better than others, and some are either very obviously meant for weapons or are even noted as being weapons-focused kata. One example is Master Asato mentioning that passai is good for defending against the bo (see Karate-Do Tanpenshu, by Patrick and Yuriko McCarthy). He didn't specify more so, but it supports the points made about the relationship between weapons / tools and karate (Ryukyu kenpo: the Okinawan version of Chinese boxing methods, particularly from the southern type of Chinese boxing). Thus, this footage shows a version of niseshi saijutsu, with further research from various sources including Mutsu Mizuho's Karate Kenpo in which he illustrated Funakoshi niseshi (or, as with any, at least a version of it).
