IP Camera's come in different forms, you can buy cheap low end versions that only run 720p at 1mp, however, through a networkable DVR, due to 3G network bandwidth, the remote viewing is crap, if you go IP camera, spend the money and go with a high end camera such as AXIS, ACTI or MOBOTIX, they offer some HD 1080p network cameras that have on board SD micro cards that you can run directly into an embedded 3G modem router or a LAN and have 1080p live feed remotely inlcuding D1 compression etc. your money would be better spent with a High Res WDR Day|Night analogue camera running an IP POE Balun ( the balun converts the anlogue signal to digital and assigns an IP address making your analogue camera networkable via cat5e/ethernet with RJ45 termination, drop this on your LAN and access via browser or app).
the security on these network cams etc is pretty good, unless people know the exact external ip address, port number and admin login details, your pretty safe.