I use my iPhone with H@me this way since it's sits on my nightstand charging every night. This has totally replaced the need to use the keypad for both me and my significant other as we both have iPhones. I arm the system every night in bed using my phone.
The only issues I have and you may see less or perhaps more depending, is when you wake up the device it takes a few seconds to connect to the WiFi and get an ip address, so if you start H@me up to quickly I have noticed it doesn't like that situation too much sometimes. That is I have had it hang for a few seconds then prompt with a dialog to reconnect, then it works, I have also had it just close H@me then I have to run again and it works. Now I am not sure if this may be worse or better on the iPhone vs iTouch, since I have it set to access either through cellular or WiFi using a DDNS name, so when starting up H@me too quickly I think it's actually starting to access the system through cellular then switching to WiFi on the fly which either H@me or the panel doesn't like. Perhaps this would be more stable on a touch thats only on WiFi then again it just might come up with a connection error until WiFi is fully connected.