I am trying one called "Dry Fire Par Timer" for Dry fire Practice. I like it, it is simple. Shot Timer Apps dont work all that well because of the sensitivity with a phone... other sounds confuse it. If you are by yourself, then it would not be an issue. I like to plug a cable into my Hearing Pro to hear the timer beep at the range.
100%, two reasons: shot timer works better and my iphone or droid phone costs about 4 timers as much as the avg timer so why risk it having laid out on a table or exposed.
PACT Club Shot Timer 3 or CED 7000, I used both of them without issues. The CED is our timer for our club matches, used and handled monthly or more for the past 3 years and none have broken.
Every shot timer app I tried resulted in frustration. I just ponied up the $120-ish for a real timer and never looked back.
Works very well, and seems to be what everyone tends to use. So you can hand it to someone and they should know how it works since they have used it before.