A few notes from a BTDT who has tried a few of them -
Woombie is genius, loved it.
The fabric high chairs that attach to regular chairs suck - they don't get the baby close enough or high enough to eat at the table with you. Get a portable booster or hook on chair instead.
Bottle Sling - big no no, same with using a pillow to prop the bottle up. Older kids it's probably not as bad for, but for littler babies who can't control the flow or push the bottle away as well it can cause them to choke.
The "real" snack/activity tray for the car seat looks like it's pretty soft, but the DIY one could be incredibly dangerous in a crash - the rule of thumb is no hard toys (they can cause *serious* injury in a crash).
Hooded car seat blanket - another no-no. You should never add anything to the car seat between the baby and the seat itself that isn't included iwth the seat. You can absolutely tuck a blanket around, but not behind the baby. For our winter babies, this is awesome:
However, this one should NOT be used, as it goes between the baby and the car seat:
A lot of the other are really great (?) ideas taht I just haven't tried or heard too much about.