Re lifejackets
The Harness on a marine one fulfils 2 purposes :- 1. To enable you to clip yourself on to a safety line so you don't fall overboard. 2. It's useful to a haul you back on with if you forgot the safety line and ended in the drink. Adds weight and not really necessary for aviation use.
T*%@#air have a "Large Display Digital Timer" for 24.99. Same one with a different label available from
RS Components (not generally the cheapest people on the block) at 15.99