As per my knowledge, upto now there is no API/WS for BSE/NSE markets.
If you wish, You can implement java stock API.
Take the data from www dot nseindia dot com .Intrude for applet ticker code. Use decompilers. You can find OHLC data links(stocks, futures, indices). Use Regular Expressions and develop stocks quote framework.
Even you can download quote data from YA HOO finance. Search for indices, findout N S E and look for Components link for NSE market. Navigate and find out download data links(future data not available). YA HOO finance NSE data is realtime.
I don't have much idea about how to implement strategies. We can take traderji's experts ideas about implementing best strategies, indicators etc...
All the best,
pajjurus