If I have the time I hope to see which of the 23 Things can be done from a smartphone, such as a Treo.
Awhile ago while waiting for a program to start I did try out Things 4 (Flickr) and 9 (Twitter)
Flickr on a mobile phone allows you view recently uploaded photos. You can also search photos by tags or keywords. While on the road I tried to sign in to my account to see what I could do and couldn't because my username has an underscore and I couldn't find the character on the keyboard. Back at the office I pulled out the manual and got signed in. Once signed in one can add comments and view photos from contacts. You can not see groups, sets, or collections. Uploading is done through email.
Twitter has a nice mobile interface. Simple, clean. You see the tweets, can update, can get to your followed.