How can I monitor bandwidth capacity over time? I know that I can use some applications such as Speedtest to check my current bandwidth capacity. However, I would like to monitor bandwidth capacity over time as I would like to assess the quality of the wifi connection around me throughout the day. Is there anyway to do so on Android?

I use Samsung Galaxy S3 with Android 4.1.2 and Nexus 7 with Android 4.4.2.
That's a pre-destined case for apps like OpenSignal, which are designed for mapping signals around you. Network Signal Info offers it as well. Both tools can be used to get a coverage map for WiFi and mobile signal, and also offer you to log signal strength.