Searing Sous-vide with electric heat gun
I doubt that it will work. A butane torch can provide a temperature of up to 1700K (1,430 °C; 2,600 °F) (according to Wikipedia), whereas I haven't seen any electric ones claiming to go above 600°C (1100°F).

While 600°C seems plenty warm to get a decent Maillard reaction going, it will take much longer than with a higher temperature, and you will probably dry out the underlying layers.

(The 'Searzall' looks like a modified butane torch, rather than an electric heat gun.)