Trying a wee experiment on my Brompton today to and from yoga. I don't have a cycling computer and use my Garmin watch for speed distance etc and is totally adequate but it has no mapping. Do I need mapping? I had to navigate to Kinetics last week from Partick and I used Google maps with my phone in my pocket. I felt it had potential and although I've been loath to risk my phone on the bikes, I bought a mount. Does seem pretty steady and secure but me being me I had a safety cord as well. I then used Google maps set to 'bike' and used an old Bluetooth headset. It actually was pretty good. Not sure how often I need nav but interesting and a very low cost solution that will do all my bikes. There may be other apps and as well as Google and I do have OS on my phone.