I am doing a project where my electronics runs on 5V which I wanted to power from a 7.2v lipo regulated down to that voltage. I'd really like to include the opportunity to charge the lipo without removing it from the project. What kind of circuit/components do I need to do it properly? Say, would putting a battery charging ic at the battery's terminals in parallel to my system be enough to achieve what I need?
Yes, but adding the device load directly to the charger load could confuse the charger IC. A better idea is to implement the load sharing system described in Microchip's AN1149: "Design A Load Sharing System Power Path Management with Microchip's Stand-Alone Li-Ion Battery Charger". This will run the device off battery power when it is standalone, and switch transparently to wall power when external power is available.