Edited after @wax eagle corrective comment
By RAW alone, it seems to be maybe to both questions.
Sneak AttackDDI is defined in terms of weapons alone: you can deliver it when hitting with a light blade, hand crossbow, shortbow or sling; but it does not explicitly limit the usage to Weapon (keyword) attacks only.
This implies that hitting with a dagger allows the use of sneak attack damage, even if the dagger itself is an implement. With regard to Ki Focus, at least 2 cases can occur.
- The dagger itself is the Ki Focus (a cherished memento).
- The Ki Focus has a non-weapon shape (a training manual) and you are enhancing your weapon with the Ki Focus magic when making a Weapon attack (see last paragraph of the Ki Focus description).
Case 1, in my opinion, leads to a straightforward yes answer (you are sneak attacking using a dagger).
Case 2, as the discussion pointed out by @wax eagle explains, is a disputed field. Rules wording is prone to multiple interpretations. On a side, following the common natural language, you are using a dagger to land a hit on your target (sneak attack bonanza); on the other you are using a power from a training manual (implement), and the dagger is a mere vessel for this power (in fact, you are not applying the dagger +3 proficiency bonus).
About Surprising Charge... I don't have access to the rules right now, but if I remember correctly, the 1[W] notation isn't tied to the Weapon keyword. So, charging with a implement-based MBA wielding a dagger-as-implement should grant the additional 1d4 die of damage; while doing the same with a dagger-infused-with-training-manual-ki is still a disputed question.