Online grocery shopping. This was before the days of 24 hour shopping, so I couldn't go after my husband got home from work. I used to dread having to do the weekly shop with three of them in tow.
To be able to "shop" online without interruption, without "mummy I need a wee", without having to referee arguments and having things surreptitiously added to the trolley, with a nice cup of tea to hand, would have been bliss.
Although I do remember when our local Sainsbury was first opened. My daughter was at school by that time, so I went along to Sainsbury with the two boys and was THRILLED to find a trolley with two child seats in it. No longer a need for chameleon eyes!