Hackable devices tips
Obtaining electronic components for cheap (or free)
http://www.zbozi.cz/
Air Wick Freshmatic imotion mini - PIR motion detector + some circuitry for 161kč
http://conrad.cz/
http://aukro.cz/
Circuit bending stuff for 20-40 kč
http://sbazar.cz/
gme.cz second floor has boxes with scrap stuff, often containing practical things like useful connectors, fine LEDs per 1CZK, etc.