that is a cool idea, and as a BitcoinHolder i am all for these kinds of long term stuff.
and i don't want to disappoint you or anything but what you are storing is already available online
for example you can visit any exchange that gives you historic data and use that to draw a line chart or even like poloniex get the OHLC data and draw an OHLC chart.
example for XMR from their API doc:
https://poloniex.com/public?command=returnChartData¤cyPair=BTC_XMR&start=1405699200&end=9999999999&period=14400there is also bitcoinity where you can get
market cap or
price and other stuff in CSV format (only for bitcoin though).