A Geyser, is a hot water heater in South Africa. There are many houses that are not connected to conventional utility grids, and heating water with electricity and natural gas is expansive and/or impractical.
Tankless, batch hot water heaters directly connected to the shower etc, are a great single-use application for an efficient stoves.
Shia Manzi
Shia Manzi has a biomass fueled - batch burning geyser
more about their biomass geyser: http://www.shizamanzi.co.za/
and through the shower installer: http://showerbizz.co.za/