Android charts: achartengine or AndroidPlot?

I haven't look at AChartEngine but have used AndroidPlot and can relay my experience here.

I've successfully had multiple lines on my chart being updated in realtime (Req 1&2) and this chart has been embedded inside of another control (Req 3).

For Req 4, I haven't worked with a db but my guess is that you would have to write the code to do the query and update the chart yourself.

I think AchartEngine is better because you have lots of flexibility. and it is a open source library.there is a good number community to help you out. It's a better library if you want different kind of bars in your application.