Originally Posted by Iride01
If you have a smartphone already, you can try some apps right now. Some have a free version with less features or a free trial period or are just inexpensive. An Wahoo
TICKR HEART RATE MONITOR strap and Wahoo
BLUE SC SPEED AND CADENCE SENSOR, both bluetooth/Ant+ will leave you positioned well if you decide to try a dedicated device later.
Lots of good advise here so no point in me repeating what others have said. However, I will comment and agree with this statement. Wahoo has a free cycling app, Wahoo Fitness, that will use any Ant+ and BTLE sensor, providing Ant+ is supported by your phone. I used my iPhone with the sensors listed above for over 4 years but I did have a Wahoo RFLKT connected to it so that I could see my ride data without having to view it on my phone. Unfortunately, my RFLKT went belly up and are no longer made by Wahoo but I have seen them still available on the net. As for the battery life, I purchased a Wahoo Elemnt Bolt to replace my RFLKT and the battery usage, per ride, is about the same as when I used the phone with the RFLKT and all the sensors connected to it.