For my needs, something like the Oregon or Montana handheld units with either and embedded AIS receiver, or linked via bluetooth from a handheld VHF / DSC / AIS, compatible bluetooth enabled transceiver would be a terrific product for kayaking in navigable waterways.
Such products are bound to appear soon, and they will be an instant market success; as many mariners, especially recreational sailors, kayaker's, etc., would rush to purchase a product such as this.
There is some concern about screen clutter, but showing AIS targets, with finger flyover revealing pertinent details on a selected vessel would present valuable information to slow moving vessels trying to cross in less than clear visibility or busy traffic areas.