There are more Blingmaster Skygod watches on the market than you could imagine.
Despite having a watch fetish (I'm now up to 9 timepieces...) the most useful timepiece I've ever had for flying is this, the ASA flight timer:
Asa Flight Timer
Two separate timers means I run one constantly for fuel, and the second one measures different legs of any navigation.
You will need to time your legs during PPL training - you will use the leg time to confirm where you are at various stages along that leg, and confirm you are on time, before your next leg.
This timer also has a clock (12H, 24H and Zulu), as has been mentioned already it is time at turning points you will need to report.
Clips neatly onto a knee board, and does exactly what it says on the tin.
Old Ben