Which perspective is this class from? Business Marketing or Engineering?
Cus I can tell you the biometric timeclock wouldn't be an incredibly complex device. Probably 4 to 5 IC chips, a microcontroller core, small graphic CoG LCD, a PCB, case and the kicker of the entire deal.. finding a thumb scanner that can take that kind of abuse, accurately and sustainably.
As for your current/voltage limiting charger, that would entirely depend on the type of battery the device in question is using as there exists different charging methods & circuits for different battery types. Either way it wouldn't be practical as you'd be proposing a design change for every proprietary charger on the market.. or a universal charger for every proprietary device on the market. Either way..... meh
If you want something cool, checkout RFID. There's a lot of cool innovation being done in that field.. some with some ethical questionability, but the technology has a lot of room to both grow and make life more convenient. Think RFID credit cards
Albeit not entirely practical.. the idea of waving your hand across a scanner for payment is kind of a cool thought.