This solar cell tree charger by Vivien Muller is kind of interesting. You can use it to recharge your cellphone, camera, or whatever, because it has 54 tiny photovoltaic panels and an internal battery that stores energy. The modular parts are connected and can be rotated infinitely creating a different tree for your favorite sunny spot at home.
Unfortunately, this design is only a concept, but judging by the web response so far, there seems to be a large contingent of folks that want to buy one. Plus, it has to be easier to maintain than a real bonsai tree — those things are tough to keep going.