I'm guessing my post will be the least popular but please don't flame me for my thoughts/choices. They are mine and I certainly wouldn't impose on others.
Wii - Age 6
Laptop - Age 7
TV - Age 8 1/2
iPad Air - Age 8 1/2
Xbox 360 - Age 8 1/2
iPhone 5s - Age 8 1/2
Our DD (9) starting navigating a desktop when she was 2 to listen to music. It was with DH or me but she was the driver. Proper controls were in place. We have always had at least 1 laptop and 3 desktops between the two of us. DD got a laptop Summer 2013 at age 7 for MineCraft and IXL (math app required by her school). She never abused the privileges and has long since abandoned it. I don't it has been turned on since Nov. 2013.
She received a Wii when she was 5 or 6 and it always stays in the main family room and it gets used sporadically.
We relocated in Dec. 2013 and DH gave her his tv. She has maybe turned it on 10 times in 9 months other than DVDs. She has a uVerse DVR box but just can't be bothered to take time to watch tv.
The school system she was in for 1/2 of 3rd grade was trying to pass an ordnance that all students must have an iPad. They used iPads heavily in the classroom and students were required to log at least 20 minutes a night on IXL.
She received an iPad Air and an Xbox 360 for Christmas 2013 at age 8. The iPad is used constantly for spelling, reading, and math. In addition, she watches
YouTube videos, streams music, chats and Skypes with friends, and plays Minecraft and Survivalcraft. She has yet to abuse any privileges.
Overall, she choses to be outside with friends or doing physically related activities. She owns over a 1,000 books because she loves to read. She chooses whatever interest her at the moment whether it be electronic, mental or physical. The electronics have their use for both learning and leisure.
I hear many concerns on protecting a child's innocence. We have found that life takes care of that in whatever manner it shall. My DH was paralyzed at age 3. She lost innocence then. My dad lived with us and died when she was 7. More innocence lost. She started riding the bus in 3rd grade. More innocence lost. At age 9 (7 days prior actually), I started the conversation on female bodies. I got out two sentences and she informed me of what I was trying to say and upon questioning, the 7 yr old boy next door had explained it to her when she asked why his sister wasn't swimming. In that conversation she also said she knew where babies came from (not truly but in her mind she knew from a tummy) and the kids on the bus had explained that. The bus only served kids in grades K-4. Seriously. More innocence lost.
She received the iPhone bc I took a job out of state and had to be away M-R night. The company provided me with an iPhone so she got my old one with unlimited minutes and data bc that is what our family plan is. It wasn't purchased for her nor meant to be exclusively hers. Without the move, she would have received a phone at middle school which would have been sixth grade and age 11. She calls family only and texts a few friends. She takes it on sleepovers and if she is playing at a friends. It works for us.